The first permanent ceasefire called by the militant Basque separatist group Eta has come into effect.
Some 800 people have died as a result of Eta's long campaign
The truce began at midnight local time (2300 GMT) amid cautious optimism across Spain that it might signal an end to 38 years of conflict.
An opinion poll published in Spain on Friday suggested overwhelming public support for negotiations with Eta.
Spain, the EU and US all consider Eta a terrorist organisation. Spain insists Eta must disarm before any talks.
The poll for a commercial radio station, Cadena Ser, found that 80% of those questioned wanted Prime Minister Jose Luis Rodriguez Zapatero to talk to Eta.
One of Mr Zapatero's cabinet colleagues, Fernando Moraleda, said Eta must first give clear signals of a definitive end to violence.
Two previous Eta ceasefires collapsed within months.
The BBC's Jim Fish in the Basque city of San Sebastian says many Basques share Eta's goal of independence but reject the group's violent methods.
It is not yet clear how a peace process will begin - and there are doubts about Eta's move because Basque politicians are divided over how to proceed, our correspondent says.
1959: Eta founded
1968: Eta kills San Sebastian secret police chief Meliton Manzanas, its first victim
1973: PM Luis Carrero Blanco assassinated
1978: Political wing Herri Batasuna formed
1980: 118 people killed in bloodiest year
Sept 1998: Indefinite ceasefire
Nov 1999: End of ceasefire, followed by more bomb attacks in January and February 2000
Dec 2001: EU declares Eta a terrorist organisation
March 2003: Batasuna banned by Supreme Court
May 2003: Two police killed in Eta's last deadly attack
Nov 2005: 56 alleged Eta activists on trial in the largest prosecution of its kind
March 2006: Eta declares permanent ceasefire
"It will be a very long and very difficult process," one San Sebastian woman said.
Eta has urged Spain and France to enter into peace negotiations.
The European Union welcomed the ceasefire, saying it was a "very positive sign".
Eta said in a statement handed to the Basque newspaper Gara on Thursday: "It is time to make important decisions, moving from words to deeds."
It called on Spain and France to seize the opportunities offered by its decision to lay down arms.
Eta has been blamed for killing more than 800 people in its fight for independence for the Basque region of northern Spain and south-west France.
Prime Minister Zapatero has said he will take time deciding how to respond to the ceasefire, which was announced on Wednesday.
He himself has warned that any peace talks will be "difficult".
"We will react with prudence to reach the end of this historic drama," he said.
Eta's activities had been waning, with the number of bombings falling in recent years. The last deadly Eta attack was in May 2003.
Some analysts said Eta's campaign became virtually untenable after the Madrid train bombings in March 2004, blamed on Islamists, caused widespread popular revulsion.
Since 1999, Spanish and French police have also carried out a wave of arrests which are said to have hit the organisation hard.