Basque separatist group Eta said today is was ending its 15-month ceasefire and issued a warning to the Spanish government of new attacks "on all fronts".
In a statement sent to Basque media, the group said it was calling off the truce because of "arrests, tortures and every type of persecution" by the Socialist government, which tried unsuccessfully to negotiate peace last year.
Ets, which has been fighting for independence for the Basque territories for four decades, declared a ceasefire in March 2006 and had insisted that it still held despite killing two people with a bomb at Madrid airport in December.
The government of Prime Minister Jose Luis Rodriguez Zapatero started exploratory peace talks in mid-2006, but broke them off at the end of the year after the airport bomb.
At the time, Eta said it had not meant to kill anyone and was only seeking concessions in peace talks.
"Eta wishes to announce that it is abandoning its permanent ceasefire and has decided to act on all fronts in defence of Euskal Herria," the group said, using the Basque language name for the Basque Country.
Mr Zapatero said the ceasefire had already been broken in December by ETA, which also called off an earlier truce in 1999. "ETA's decision is absolutely the opposite of what Basque and Spanish society want: the road to peace," Mr Zapatero told reporters. "Spanish society has shown over a long period that pain does not sap its strength, that suffering does not reduce its determination."
Eta killed more than 800 people in four decades of armed struggle for independence. Most Basques do not want to secede from Spain, polls show, and the Basque Country already enjoys considerable autonomy.
Eta's banned political party ally Batasuna, which was not allowed to take part in last month's regional elections, appeared to distance itself from violence.
"Breaking the ceasefire was exclusively the responsibility of Eta," Batasuna leader Arnaldo Otegi told a news conference in San Sebastian while blaming the Spanish government for the collapse of the peace process.
More than 700 arrests in Spain and France since 2000 have seriously weakened Eta, which also lost support after Islamist bombings in Madrid in 2004 increased public revulsion against terrorism, security services believe.
The Eta decision was described by Minister Foreign Affairs Dermot Ahern this evening as "deeply disappointing".
"While the practical implications of today's announcement remain unclear, this is a retrograde step which can only delay the final resolution of a conflict which has scarred the lives of so many," Mr Ahern said.
"Eta's leadership and all those with influence over it should reconsider, and commit themselves to work for a resolution of all outstanding problems by purely peaceful and democratic means."