The Spanish government on Monday hailed as a "historic" victory against armed Basque separatist group ETA the weekend arrest in France of ETA's political leader and 16 associates, the worst blow the underground group has suffered for more than a decade.
"This is a major step towards ending the violence of the terrorist group ETA. ETA's destiny can only be its demise," Spanish Prime Minister Jose Luis Rodriguez Zapatero told reporters.
Zapatero offered his "deepest and most cordial congratulations" to the French authorities for their operation and added that ETA had "to understand that, in a democracy, political objectives can only be laid down through words and ideas, never through violence."
Spanish Interior Minister Jose Antonio Alonso earlier saluted the "excellent relations between France and Spain," which he said had been instrumental in bringing about the breakthrough against the group.
Florencio Dominguez, an expert on Basque affairs, told AFP that whereas ETA had managed to bounce back from previous "decapitations of its leadership," "this time it will do so with much less force."
The Spanish political establishment's optimism came the day after French authorities reported the arrest of 17 people including Mikel "Antza" Albizu Iriarte, ETA's political leader and chief theoretician, and his partner, Soledad "Anboto" Iparragirre Genetxea, a suspected former military chief of the group, in the Pyrenees-Atlantiques region near the Spanish border.
Spain's public prosecutor has called for Iparraguirre, suspected of more than a dozen killings, to be extradited to Spain, judicial sources said Monday.
The sources added that Spanish judge Baltasar Garzon would seek to question "Antza" in France, having four years ago opened an investigation into the same suspect for "belonging to an armed group."
On Sunday, the French interior ministry said arms caches were discovered in seven locations after around 140 specialist officers, including members of France's anti-terrorist brigade and intelligence services, raided several properties.
Alonso said the French raids turned up 400 kilograms (880 pounds) of dynamite and 300 kilograms of potassium chlorate.
The swoop on the suspected Basque militants was the biggest setback ETA has suffered since 1992 when a raid in the village of Bidart in the same area of south-west France netted the entire leadership of the organisation.
ETA, which has been fighting for an independent Basque homeland since 1959, has killed 817 people in the process, according to a count released Monday by El Pais daily.
But 12 low-level attacks this year have not led to any fatalities.
Since "Antza" became ETA's political leader following the Bidart arrests 120 people have been killed while 1995 saw unsuccessful attempts to assassinate King Juan Carlos and former prime minister Jose Maria Aznar, then still opposition leader.
"Antza" was ETA's negotiator in talks with the government during the 14-month truce declared by ETA in 1998. After the Madrid train bombings this year, initially and wrongly blamed on ETA, in which 191 people died, the organisation moved to what the regional Basque government called "low intensity warfare."
Sunday's operation followed the arrest in April of ETA's logistics chief Felix Ignacio Esparza Luri and ETA's logistical, political and military co-ordinator Felix Alberto Lopez de la Calle.
Spanish officials said that a total of 21 suspected guerrillas were detained in all over the weekend, that count including those detained in France and also four others who Spanish police said Saturday they had arrested last week on the Spanish side of the border.
The Basque country straddles the two countries, comprising a large region of northern Spain and part of south-west France.