Eta, the armed Basque separatist group, today announced an end to its 15-month ceasefire, dashing hopes of resolving a four-decade violent conflict centred on the north of Spain.

Until now, Eta had insisted that its “permanent” ceasefire remained in place, despite exploding a bomb at Madrid airport in December that killed two people. At the time, Eta said it had not meant to cause any deaths and blamed the authorities for failing to fully evacuate the car park after telephone warnings.

From midnight tonight, Eta said that it would suspend the ceasefire and “act on all fronts in defense of the Basque Country”.

Authorities are bracing themselves for a possible summer bombing campaign in Spanish tourist spots. Eta has previously targeted tourist resorts in an effort to draw headlines and damage one of Spain’s most important industries.

But it has generally sought to avoid the sort of large-scale casualties among tourists that could cause it to lose support in its heartland. Even so, two people died and more than 50 were injured in Eta’s summer bombing campaigns in Valencia following the end of its previous ceasefire in 1999.

For Spain’s Prime Minister, José Luis Rodríguez Zapatero, the news is an important political setback with just nine months to go until the general election. The Socialist leader had bet heavily on achieving peace in the Basque Country, the third Spanish Prime Minister to have tried and failed to broker a deal with Eta.

Despite Eta’s move, Mr Zapatero vowed today to continue to work for peace in the Basque Country.

“The decision by Eta goes radically against the path wanted by both the Basque Country and Spanish society - the path of peace,” Mr Zapatero said. “I am convinced that, sooner or later, the Spanish people will secure peace definitively. I will work to ensure it is reached as soon as possible.”

The Opposition Popular Party (PP) has relentless criticised Mr Zapatero’s negotiations with Eta and its political allies, despite the fact that the party attempted the same feat when it was in Government. The PP has mounted street demonstrations hundreds of thousands strong, in which Mr Zapatero was denounced as a “traitor” for having “surrendered to terrorists”.

Eta also laid the blame for its decision to return to violence squarely on Mr Zapatero. The Government recently got Spanish courts to strike off around half the candidates of a radical Basque separatist party called ANV after deciding that they were linked to the Eta’s outlawed political ally, Batasuna.

The move did not go far enough for the PP, which had wanted the entire party to be outlawed. But Eta today used it to justify abandoning its ceasefire, saying that that the Prime Minister’s “fascism” had left Basque citizens “without rights”.

It also railed against the Basque Nationalist Party (in Spanish: PNV) that governs the region, accusing the moderate nationalist party of being traitors. The PNV had refused to allow the Spanish Government to enter into any substantive political negotiations with Batasuna until it clearly rejects the use of violence.

The Basque government today called Eta’s statement “a macabre joke” that ignored the wishes of most Basques. “In whose name does Eta act?” asked Miren Azkarate, a spokeswoman. “Certainly not in the name of the Basque people.”

Eta has been keen to show in recent months that it is ready to act. Videos have emerged showing masked members forging identity cards and preparing bombs.

During the ceasefire, it stole 350 guns from a French factory and Spanish police have found explosives in Basque Country arms caches. It also emerged that Eta had again begun sending extortion letters to Basque businesspeople to raise new funds.

Tony Blair has given his strong backing to Mr Zapatero’s efforts to bring about an end to violence in the Basque Country. The two have spoken repeatedly about the issue and Mr Zapatero has sought to draw lessons from the peace process in Northern Ireland.

Eta began its campaign of violence in 1968 against the dictatorship of General Franco, who banned the Basque language and had long punished the region for opposing him in the Spanish Civil War. The bulk of the group layed down its weapons after Franco died in 1975 and Spain returned to democracy, but a hard-core have kept-up a campaign of violence and intimidation that has cost more than 800 lives. The group is considered a terrorist group by Spain, the US and the European Union.

The Basque region, which straddles the French and Spanish border in the Western Pyrenees, has its own distinctive language and culture. A recent poll showed that around 15 percent of Basques sympathised with Eta’s goal of an independent Basque homeland, though only 1 percent said they agreed with its violent methods. A further 19 percent said that Eta had been justified during Franco’s dictatorship, but not any more.

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