Basque terrorists launch 'last-ditch' campaign

A spate of terrorist acts is seen here as a last-ditch effort by separatists to oust security troops from Spain's Basque region.

Spaniards are still holding their breath after terrorists blew up a key telephone exchange in Madrid on April 18. The explosion left the capital practically without phones and cut off from 11 provinces. The bombing was believed to be carried out by the Basque separatist organization ETA (Basque Homeland and Freedom).

Only 20 hours later, suspected Basque guerrillas attacked a Civil Guard barracks with hand grenades and guns in San Sebastian early April 19. The attack in that Basque city barely missed adding more victims to a growing list of casualties.

In the week preceding the telephone-exchange bombing, there were five attacks with Soviet-made grenade launchers that killed one person and wounded nine others. Since the end of January, 12 have been killed.

On April 16, ETA issued an ultimatum giving the Spanish government 30 days to withdraw all security forces from the Basque region.

With the court martials of last year's coup plotters nearing the final stages , the escalation of Basque violence ''constitutes a good contribution to the defense of the plotters on trial'' says Juan Maria Bandres, leader of the radical Basque legal political party, Euzkadiko Ezkerra (EE).

The coup plotters have continually referred to intolerable separatist violence as the reason for their rebellion. ETA recently has been losing popular support and sympathy, according to Madrid's independent daily El Pais. The guerrillas' strategy now seems to be to stir up passions within the armed forces in hopes of generating support for a military dictatorship in which ETA would gain popularity.

Politicians from all parties concur that the attacks are a deliberate attempt to provoke the armed forces. Tensions are still strained as the coup trials drags into its third month.

According to Interior Minister Juan Jose Roson, ''ETA wanted political destabilization at an especially delicate time. . . .'' Socialist leader Felipe Gonzalez says, ''Terrorism has to look for its own justification through a dictatorship.''

Carlos Garaicoetxea, premier of the regional Basque government, has expressed indignation at the attacks and warned that terrorists intend to ''sink'' democracy. Spanish politicians all seem to be pleading for serenity and defending democracy.

The ease with which the guerrillas blew up the four-story telephone exchange, causing $10 million in damages, demonstrated that the security of strategic communications centers is somewhat precarious.

Although Mr. Roson claims the ETA is using 40 or 50 of its militants in a final offensive, the bombing appeared to many as a significant show of strength.

With the World Cup soccer matches beginning June 13, one month after the ETA ultimatum ends, the government is responding with an all-out offensive. Military chiefs met April 19 to complete plans for stepping up security operations.

New security measures have taken around installations to prevent another communications collapse. Police are on alert throughout the country and the armed forces have stepped up a watch on the French border.

Government officials say that allowing the military a larger role in fighting the ETA would free police and paramilitary Civil Guards to hunt the guerrillas. But giving the armed forces a key role in internal security is a sensitive issue in Spain, where the 40-year military dictatorship of Gen. Francisco Franco ended less than seven years ago.