Gal's mission was to destabilise Eta in its "safe havens" across the border in France.

Made up of members of the security forces and hired assassins, Gal (Anti-terrorist Liberation Groups) was responsible for 28 murders between 1983 and 1987.

The first action that Gal claimed responsibility for was the kidnapping of an alleged Eta activist, Segundo Marey. He was held for several days and threatened with death.

However, he was released 10 days later - when it became clear that he was unconnected to the group.

But his captors issued a warning that they would kill an Eta member for every murder by the separatists.

Orders from the top

The government's involvement in this shadowy armed group has been the subject of a judicial inquiry and a Supreme Court trial which has convicted two senior government ministers.

It was for ordering and financing Mr Marey's kidnapping that the former interior minister Jose Barrionuevo and his security chief were jailed for 10 years.

Eta and other Basque organisations have always maintained that the Socialist government of Felipe Gonzalez was orchestrating the "dirty war" against them.

But the former prime minister and members of his cabinet denied all knowledge of the dirty war.

The dam begins to leak

Then, in the late 1980s two senior policemen were arrested and later convicted of recruiting hitmen and funding Gal attacks.

At first they refused to name others involved, but after serving four years of their sentences, they began to reveal more details.

This led to a judicial inquiry in 1994, and later the Supreme Court trial - which is the first of many probing the extent of the government's involvement in the death squads.

A direct link

The trial established what has long been suspected - that Gal was financed by secret funds from the Interior Ministry.

Correspondents say the Spanish people would have overlooked the government's involvement - had it not been that more than a third of the people killed by the Gal death squads had no connection to Eta.

Various newspaper investigations have also added to the intrigue.

The Spanish daily El Mundo reported that agents from the Spanish military intelligence organisation Cesid were involved in Gal.

It claimed that Cesid agents kidnapped a beggar and two drug-addicts as medical guinea-pigs in preparation for the kidnapping of a leading Basque terrorist, and dubbed their kidnap plan Operation Mengele - after the Nazi doctor who carried out medical experiments on Jews, vagrants and other victims of the Holocaust.