Spain's prime minister has said he is suspending all moves towards dialogue with Basque separatist group Eta after a car bomb attack at a Madrid airport.
Mr Zapatero said the bombing was a massive mistake by Eta
At least 19 people were injured and two are missing after the blast in the car park of Barajas Airport.
Jose Luis Rodriguez Zapatero said this was the rebels' worst mistake but did not announce ending the peace process.
A spokesman for the group said peace talks were needed more than ever. Eta called a ceasefire nine months ago.
The blast brought several floors of the multi-storey car park at Madrid's international airport crashing down on top of each other and left vehicles covered with rubble and glass.
Several floors of the multi-storey car park collapsed
Officials said the armed separatist group, Eta, had made a call to claim the attack.
Mr Zapatero said the bombing was "utterly incompatible" with the ceasefire, announced in March. "Today's is the most mistaken, futile step which the terrorists could take," he told a news conference.
"I have decided to suspend all initiatives for dialogue with Eta," he added.
But, from the city of San Sebastian, the leader of the banned political party Batasuna - regarded as a mouthpiece for Eta - denied that the peace process was damaged, saying it was now "more necessary than ever".
Arnaldo Otegi said dialogue was the only "reasonable and democratic alternative" to "definitively change the situation in our country".
But the BBC's Danny Wood, in Madrid, says that after the bomb attack talks seem a long way off.
The Eta ceasefire was declared in March after four decades of violence aimed at creating an independent Basque state in the north of the country.
The bomb exploded at about 0900 (0800 GMT), causing minor injuries to at least 19 people including two police officers and a taxi driver, emergency services said.
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
The authorities had time to evacuate the area, but two person remain missing. The bomb significantly damaged the car park, sending a huge plume of smoke over terminal four.
Flights in and out of terminal four were halted for a few hours.
In March, Eta declared that it was permanently ending an armed campaign that has killed more than 800 people.
In response, Mr Zapatero announced the beginning of talks with the militant separatist group, although discussions have not officially started.
Victims' associations and the conservative opposition are renewing their demands that the government immediately call off the peace process, our correspondent says.