A powerful car bomb exploded Monday in northern Spain, killing an army officer and wounding six other people in the third attack in 24 hours by suspected members of the Basque separatist group ETA.

And in France, police detained six suspected Basque militants in a probe into the financing of terror attacks in France and Spain.

The attack Monday in the northern town of Santona signaled a new ETA offensive just days after the Spanish Supreme Court outlawed two Basque pro-independence parties on grounds they are linked to ETA. The blast, outside an army academy, blew a huge hole in the ground and caused major damage to buildings and cars in the area.

The Interior Ministry said the explosion occurred shortly after 1 a.m. as the building was being evacuated because of an ETA bomb warning call.

The explosion killed Sergeant-Major Luis Conde de la Cruz, 46. An army captain who was among the six people wounded was in serious condition, a ministry official said. The blast happened as people were being evacuated from the army academy and other buildings following a bomb warning call in the name of ETA to authorities in the neighboring Basque region.

The officer killed had been on holiday with his wife in Santona, staying at the academy, and was normally stationed in the central city of Segovia.

"He was a good person. He died doing what he liked most, which was to travel," Conde la Cruz's son Ivan told reporters, his voice quivering. "I just want to say one thing: ETA is never going to have its way. Never."

"Today, ETA has killed once again and has sown pain and horror in a corner of Spain," said Prime Minister Jose Luis Rodriguez Zapatero. "It has done it in its customary manner, regardless of the consequences and seeking the most damage possible."

Spain, he added "will never yield to the dictates of the terrorist group ETA. It will force the assassins to face the weight of the law and justice."

Interior Minister Alfredo Perez Rubalcaba and Defense Minister Carme Chacon flew to the town of Santona on Monday. Rubalcaba told reporters police believed the three cars used had been stolen and prepared in France.

French police said they had arrested six suspected Basque militants Monday in southwest France.

Investigators were looking at whether the suspects were linked to explosions in 2006 that slightly damaged a hotel owned by acclaimed chef Alain Ducasse.

ETA has been conducting shootings and bombings since 1968 for an independent Basque state in northern Spain and southwestern France. It has killed more than 825 people.

ETA declared a cease-fire in March 2006 but reverted to violence in December of that year after peace talks with the government failed.

On Sunday, a car bomb exploded next to the headquarters of a bank on the outskirts of the Basque capital of Vitoria. It caused damage, but no one was reported injured. Several hours later, a second car bomb in the Basque town of Ondarroa exploded outside a police station, wounding three officers and seven civilians.

ETA normally claims responsibility for its attacks in statements weeks later.

So far this year, the group has taken credit for killing a former town councilor and a Civil Guard officer.

In recent months, it has mostly set off small bombs in seaside resorts.

The northern Basque region is one of 17 semiautonomous regions in Spain and among the strongest economically. It has its own language and culture and is home to strong nationalist sentiment.