ETA, the Basque separatist organisation, announced a permanent ceasefire yesterday, to begin tomorrow.

The dramatic announcement by one of Europe’s most enduring terrorist groups marks the apparent end of four decades of violence that has claimed more than 800 lives. Three Eta members — one a woman — dressed in traditional Basque capuchas and white masks, announced the ceasefire in a video released through a Basque television station.

“Eta has decided to declare a ceasefire, which will come into effect on Friday and will be permanent,” they said in a statement. The aim is to promote a democratic process in Euskal Herria (the Basque Country) and to build a new framework in which our rights as a people will be recognised . . . At the end of the process, Basque citizens should have their say and decide on their future.”

The statement continued: “Eta also calls on the Spanish and French authorities to respond positively to this new situation, leaving their repressive ways behind.”

Commentators attributed Eta’s decision to a collapse in its support after the terrorist attacks in America of September 11, 2001, and in Madrid on March 11, 2004, the arrests of many of its leaders and the willingness of Spain’s Socialist Government to negotiate provided that the organisation renounced violence.

Most ordinary Spaniards greeted the announcement with delight, calling radio and television shows to express their pleasure. Carmen Marichalar, a Madrid tourism office official, said: “I can’t believe it. I think it’s brilliant. Now they can negotiate and bring an end to this terrorism which has gone on for so long in Spain.”

José Luis Rodríguez Zapatero, the Prime Minister, expressed cautious optimism. “The Government’s position is one of caution and prudence . . . Any peace process after so many years of horror and terror will be long and difficult,” he told Parliament. “We were united in the face of the horror. I am confident that now we are united in hope.”

But the conservative Popular Party (PP), which waged war on Eta until it lost power three years ago, dismissed the announcement. “This ceasefire is a pause, not a renunciation of violence,” Mariano Rajoy, the PP leader, said. “Eta has not asked for forgiveness from its victims, but instead intends to carry on existing.”

José Alacaz, president of the Association of the Victims of Terrorism, said: “We should be very careful, because this is a trick . . . Eta wants to get what it couldn’t get with 800 deaths: self-determination.”

Eta has announced ten previous ceasefires, the last being in 1998, only to return to its campaign of violence a year later. But never before has it described a ceasefire as per- manent.

Manuel Alcántara, Professor of Political History at the University of Salamanca, said: “The text doesn’t impose any conditions, which is significant. The next step is that we need Batasuna (the banned political wing of Eta) to accept the terms and condemn the use of violence.”

Eta has killed 817 people since 1968, when it started its campaign for a separate state in northeast Spain and southwest France. It has financed its activities through extortion and blackmail.

Its deadliest attack was the 1987 bombing of a Barcelona supermarket, which killed 21 people. It tried to assassinate José María Aznar, the former conservative Prime Minister, while he was opposition leader. But since 2003, when it murdered two police officers in the northern town of Sangüesa, it has detonated only small bombs and killed no one. Eta has been crippled in recent years by a string of arrests of leading members — the result of improved co-operation between Spanish and French anti-terrorist police. Another key reason for the ceasefire has been the dramatic change in the political climate in Spain after the 9/11 terrorist attacks in America and the Madrid train bombings by Islamic extremists, in which 191 people were killed. Those attacks provoked revulsion towards terrorism and destroyed Eta’s support even in the Basque Country.

Unlike the previous conservative government, Señor Zapatero’s administration has signalled its willingness to talk to Eta. Last May the Spanish parliament passed a law allowing it to negotiate with Eta if it renounced violence. Yesterday’s ceasefire was warmly welcomed by Gerry Adams, the Sinn Fein president whose republican movement has had close links with Eta.

“Eta’s announcement provides all sides to the conflict with an opportunity of historic proportions,” he said. “There is a particular onus on the Spanish Government to respond positively and creatively.”

One figure who appears to have played an intriguing backroom role is Father Alec Reid, the Belfast priest who helped to prepare the ground for the Good Friday agreement in Northern Ireland. Since last year, he has been involved in talks between Basque nationalist parties and the main political groups in the region.