The Spanish government warned on Tuesday that the Basque extremist group ETA (Euskadi Ta Askatasuna  - Basque for "Basque Homeland and Freedom") might launch a retaliatory attack after the arrests in France and Spain on Monday of six of its members, including its suspected leader. The arrests mark a further weakening - but not the end - of the Basque separatists.

The arrests of the suspected members of ETA mark a victory for France and Spain, and for the stepped up cooperation between the two in fighting the Basque extremist group. ETA is blamed for the deaths of more than 800 people in its 40-year struggle to establish an independent Basque state.

Among those arrested in twin police nabs on both sides of the border was the suspected new leader of the organization, Aitzol Iriondo Yarza, who goes by the name of Gurbitz. He was arrested in France, along with two other suspected ETA members. Another three were arrested across the border in Spain.

In an interview on French radio, French Interior Minister Michele Alliot-Marie hailed the arrests as the fruit of stepped up cooperation between France and Spain to crack down on the terrorist movement.

Alliot -Marie said law and order officials were getting ever closer to capturing the major 20 leaders of ETA. Last month, France arrested the suspected former leader of ETA's terrorist operations.

But terrorist experts warn that while greatly weakened over the last few years, the Basque extremist group has a capacity to nurture new leaders among its members. And over the years it has demonstrated a tenacity of staying and sowing terror in Spain. It was most recently blamed for assassinating a 71-year-old Basque businessman in northern Spain last week.

On Tuesday, Spain's  interior minister warned ETA was likely to cary out another strike in retaliation for the latest arrests.