Timeline: Eta campaign

Car bombing has been a favourite tactic of the group

The BBC News website traces Eta's four-decade campaign for a sovereign Basque state, which has cost more than 800 lives.

• 6 August, 2009: Juan Manuel Inciarte, 55, suspected of killing five policemen and the pregnant wife of one of the officers, is arrested in Madrid after being deported from Mexico.

• 30 July, 2009: Just a day after the Burgos attack, a Civil Guard barracks in Majorca is bombed. Two officers are killed.

• 29 July, 2009: A massive car bomb explodes outside a barracks of the paramilitary Civil Guard in the northern Spanish city of Burgos, injuring dozens with broken glass. Officials say it is a miracle that no-one was killed.

• 19 June, 2009: A senior police officer is killed when a bomb is attached to his car in Bilbao.

• 19 April, 2009: Jurdan Martitegi, described as the military leader of Eta, is captured in south-western France.

• 10 April, 2009: Senior Eta figure Ekaitz Sirvent Auzmendi detained in Paris carrying a Magnum revolver and false ID.

• 6 April, 2009: French police uncover a "bomb factory" in the south-eastern city of Grenoble.

• 9 February, 2009: A van explodes near a conference centre and railway line in eastern Madrid, causing no injuries.

• 31 December, 2008: A car bomb explodes near the offices of a Basque television station in Bilbao.

• 8 December, 2009: Aitzol Irionda, suspected of being Eta's new military chief after the arrest of Txeroki, is arrested in south-west France.

• 3 December, 2008: A businessman linked to a high-speed rail link opposed by Eta is shot dead in Azpeitia in the Basque region.

• 24 November, 2008: Txeroki is charged over the 2006 Madrid airport bomb.

• 17 November, 2008: Eta's suspected military chief, Garikoitz Aspiazu Rubina, alias Txeroki, is arrested in southern France.

• 30 October, 2008: A car bomb explodes in a university car park in Pamplona, northern Spain, injuring 15 people. Local officials blame Eta for the attack.

• 21 September, 2008: A car bomb blamed on Eta explodes near a military academy in the northern town of Santona, killing an army officer and injuring several other people. It comes just hours after two separate bomb attacks in the Basque region injure 11 people.

• 16-18 September, 2008: The Supreme Court bans two Basque political parties accused of acting as a front for the militants - the Communist Party of the Basque Lands (PCTV) and Basque Nationalist Action (ANV).

• 2 August, 2008: Eta's De Juana Chaos is freed from jail after serving 21 years for killing 25 people. He was sentenced to more than 3,000 years in jail 1987, but under the penal code then in force, the maximum term he could serve was 30 years. His release sparks outrage.

• 20 July, 2008: Five bombs explode in northern Spain, including four at popular seaside resorts. No-one is seriously hurt, but a woman is treated for shock. Officials say Eta warned of the attacks.

• 21 May, 2008: Eta's most senior commander, Javier Lopez Pena, is arrested in a joint Spanish-French operation in the French city of Bordeaux.

• 7 March, 2008: Former Socialist councillor, Isaias Carrasco, is shot dead outside his home in the Basque Country - two days before Spain's general elections. Prime Minister Jose Luis Rodriguez Zapatero blames Eta for the attack.

• 19 December, 2007: Spain's anti-terrorism court sentences 47 people to prison terms of between two and 20 years over their links to Eta. Those convicted are part of a network of social, political and youth organisations that back Basque separatism.

• 1 December, 2007: A Spanish undercover policeman is killed and another hurt after being shot by suspected Eta members during a surveillance operation in south-western France. The second policeman dies of his injuries within days of the attack.

• 5 October, 2007: Spanish police arrest almost the entire alleged leadership of Eta's banned political wing, Batasuna, on charges of "glorifying terrorism".

• 9 September, 2007: Eta says its campaign of violence will continue until it achieves its aim of self-determination for the Basque country. In its first statement since calling off the ceasefire in June, the group vows to "strike at Spanish state structures on all fronts".

• 1 September, 2007: Four suspected members of Eta, including a man said to be its leading bomb maker, Luis Ignacio Iruretagoyena, are arrested in a raid in Cahors, France. The group allegedly carried out the fatal bombing at Madrid airport in December.

• 26 July, 2007: Eta's suspected logistics chief, Juan Cruz Maiza Artola, and two other alleged members are arrested in Rodez, France.

• 8 June, 2007: Spanish Prime Minister Jose Luis Rodriguez Zapatero admits holding "direct and indirect contacts over a short period" with Eta since the Madrid airport bombing, but says the group had made unacceptable political demands.

• 6 June, 2007: Eta ends its "permanent" ceasefire with the Spanish government and promises to defend the Basque country "with weapons and on all fronts". Spanish Prime Minister Jose Luis Rodriguez Zapatero condemns the move.

• 8 April, 2007: Eta says it is ready to make new commitments to peace if Spanish authorities end "attacks" against it. The government replies by saying Eta "only has to take one single step: renounce violence".

• 31 March, 2007: Spanish police smash an Eta commando unit thought to have been behind 24 attacks in Spain between 2004 and 2006. Eight people are arrested and bomb-making material is seized in the major operation.

• 14 January, 2007: Hundreds of thousands of people demonstrate in Madrid and Bilbao in protest against the bombing of Madrid's airport in December by Eta. The marches for peace are boycotted by the opposition Popular Party and by a group representing victims of Eta attacks.

• 9 January, 2007: Eta formally acknowledges it carried out the bomb attack at Madrid airport in December, but says the "permanent ceasefire" announced in March remains in effect.

• 2 January, 2007: Spanish Interior Minister Alfredo Perez Rubalcaba declares the peace process "broken, liquidated, finished".

• 30 December, 2006: A bomb brings down a car park at Madrid's Barajas airport. Two people are missing, presumed dead. The government blames Eta.

• 22 March, 2006: Eta declares a permanent ceasefire, scheduled to begin two days later.

• 20 March, 2006: Eta claims responsibility for a spate of bombs planted to coincide with a regional general strike called by Batasuna.

• November 2005: Spain puts 56 alleged Eta activists on trial in Madrid - the largest ever such prosecution.

• October 2005: Eta's suspected second-in-command, Harriet Aguirre, is arrested in France.

• October 2004: Mikel Albizu, known as Antza, one of Eta's top leaders, and his partner, Maria Soledad Iparraguirre, are detained in a swoop in south-western France.

• March 2004: Eta initially accused of being behind the 11 March Madrid bombings, which are later linked to Islamist groups.

• December 2003: Police recapture suspected Eta logistics chief Ibon Fernandez Iradi in the French town of Mont-de-Marsan.

• November 2003: Spanish police arrest 12 suspected Eta leaders in a series of raids.

• July 2003: Bombs explode within minutes of each other in the Spanish resorts of Alicante and Benidorm, injuring at least 13. Five days later another bomb rips through a car park at Santander airport.

• May 2003: Two policemen are killed by a bomb in Sanguesa, northern Spain, in Eta's last deadly attack before its 2006 ceasefire.

• May 2003: The United States declares Batasuna a terrorist group. The European Union follows suit a month later.

• March 2003: Spain's Supreme Court bans Batasuna permanently in response to a government request. It is the first time since Franco died in 1975 that a political party has been banned in Spain.

• February 2003: The Spanish Government shuts down Basque newspaper Euskaldunon Egunkaria on the grounds that it is linked to Eta - but a new Basque newspaper, Egunero, hits the stands the next day, under the headline "Shut but not silenced".

• December 2002: Suspected Eta logistics chief Ibon Fernandez Iradi escapes from police custody in southern France only three days after being captured near the Spanish border.

• September 2002: French police arrest a man and woman suspected of being top leaders of Eta following a joint operation with Spanish police. The man, Juan Antonio Olarra Guribi, is believed to be the group's military head.

• August 2002: Judge Garzon suspends Batasuna for three years on the grounds that it is part of Eta, which he declares "guilty of crimes against humanity". Parliament, meanwhile, votes to seek an indefinite ban on Batasuna.

• July 2002: Judge Baltasar Garzon orders the seizure of 18m euros in assets belonging to Batasuna.

• December 2001: The European Union declares Eta a terrorist organisation - the first time all 15 member governments have labelled Eta as such, in a significant diplomatic victory for the Spanish Government.

Politicians targeted

• November 2001: Judge Jose Maria Lidon is shot dead in Bilbao less than 24 hours after a car bomb injures nearly 100 in Madrid. Lidon - who was not on any known Eta hit list - had sentenced six Eta sympathisers to long jail terms in 1987.

• May 2001: Senior Popular Party member Manuel Jimenez Abad is shot dead in the city of Zaragoza a week before elections to the Basque parliament.

• March 2001: Socialist party politician Froilan Elexpe is shot dead in an apparent Eta attack near the city of San Sebastian.

Violence resumes

• November 2000: King Juan Carlos strongly condemns Eta in a speech on the 25th anniversary of his accession to the throne. The king's unusually political address comes two days after a former government minister is killed in Barcelona.

• August 2000: Thousands of people demonstrate in support of Eta in the city of Bilbao after four members of the group die in a blast caused by explosives in a car they are driving.

• May 2000: King Juan Carlos and Queen Sofia lead thousands of Spaniards in a nationwide silent vigil to protest against the killing of journalist Jose Luis de la Calle. It is the first time the king has made such a gesture, a royal spokesman says.

• Spring 2000: The Spanish film Yoyes, a fictional film based on the story of real-life Eta operative Dolores Gonzalez Catarian, breaks the long-standing taboo in Spanish cinema against dealing with the separatist movement.

• January and February 2000: Car bombs explode in Madrid and the Basque capital Vitoria heralding a return to the violent separatist campaign.

Cross-party talks

• November 1999:The separatist group announces an end to its 14-month ceasefire in a Basque newspaper, blaming lack of progress in talks with the Spanish Government.

• August 1999: Prime Minister Jose Maria Aznar accuses Eta of being "scared of peace" and calls on the group to prove its commitment. Eta subsequently confirms that contact with Madrid has been severed.

• May 1999: The first and only meeting to date between Eta and the Spanish Government in Zurich, Switzerland.

• September 1998: Eta announces its first indefinite ceasefire since its campaign of violence began, effective from 18 September.

• June 1998: Car bomb kills Popular Party councillor Manuel Zamarreno.

• April 1998 Northern Ireland peace agreement signed. Eta is understood to have been heavily influenced by the Northern Ireland peace process. Eta has traditionally had relations with the Irish republicans and the political wing Herri Batasuna has been schooled by Sinn Fein on strategy for negotiation.

• March 1998: Spain's main political parties engage in talks to end violence in the Basque region. The government is not involved.

Leaders jailed

• February 1998: Herri Batasuna elects new provisional leadership.

• December 1997: 23 leaders of Herri Batasuna jailed for seven years for collaborating with Eta. The case centres on an video featuring armed and masked Eta guerrillas, which the party tried to show during general election campaign. This was the first time any members of the party have been jailed for co-operating with Eta.

New government

• July 1997: Eta kidnaps and kills Basque councillor Miguel Angel Blanco, sparking national outrage and bringing an estimated six million Spaniards onto the streets.

• 1997: Start of Eta's campaign against local Popular Party politicians.

• March 1996: Right-wing Popular Party wins general election. There is speculation that the change of government would lead to a crackdown against Eta, which later proves wrong. But Eta apparently views the Popular Party as heir to General Franco's dictatorship.

Violence continues

• 1995: Attempt to assassinate the leader of the opposition Popular Party (later Prime Minister), Jose Maria Aznar, with a car bomb.

• June 1987: Twenty-one shoppers are killed in an attack on a Barcelona supermarket. Eta apologises for the "mistake".

• 1980: 118 people are killed in Eta's bloodiest year so far.

• 1978: Eta's political wing Herri Batasuna is founded.

Franco years

• December 1973: Basque nationalists assassinate Prime Minister Admiral Luis Carrero Blanco in Madrid in retaliation for the government's execution of Basque militants.

• 1968: Eta kills its first victim, Meliton Manzanas, a secret police chief in San Sebastian.

• 1961: Eta's violent campaign begins with an attempt to derail a train transporting politicians.

• 1959: Eta is founded with the aim of creating an independent homeland in Spain's Basque region. The full name of the organisation - Euzkadi Ta Askatasuna - means Basque fatherland and freedom.

• 1937: General Franco occupies Basque country. The Basques had enjoyed a degree of autonomy which they now were denied. Franco regime ruthlessly represses their aspirations for independence.