President Raul Alfonsin declared all-out war on leftist subversion after touring a suburban army base where at least 36 people were killed in a battle between troops and besieged civilian commandos.

Troops were still scouring the smoldering rubble of the ravaged La Tablada base Tuesday night as Alfonsin told the nation the attack was "a new challenge that I believe is the most serious and decisive of my administration."The 3rd Infantry Regiment base was seized Monday by heavily armed civilians and retaken a day later by army and police forces who had pummeled commando positions with howitzers, mortars, grenades and machine-gun fire.

In his nationally broadcast speech, the president recalled his impressions of the base and the charred and mangled corpses he encountered there: "It was a nightmare. Death, once again death. The brutality, the barbarity."

He said seven soldiers, one policeman and 28 commandos were killed and that all but four of the 67 wounded were soldiers and policemen.

Authorities said troops captured 14 of the commandos, who apparently intended to steal weapons from the base and quickly flee.

Alfonsin described the attackers as "irregular elements of ultra-leftist affiliation," citing a written proclamation found at the base as "evidence of their hallucination."

A copy of the proclamation given to reporters said the base was seized to pre-empt a purportedly imminent coup by right-wing army officers.

"We are fed up with the arrogance of the military," it said.

Alfonsin was elected in 1983 to end a nearly eight-year military dictatorship during which 8,900 suspected leftist subversives were arrested and vanished, presumably murdered by security forces.