The attack occurred near a Civil Guard barracks in Palmanova on the western coast of the island.

Two Civil Guard officers, aged in their twenties, were killed after the vehicle that they entered exploded. The bombers, suspected of belonging to the Basque separatist group ETA, are believed to have triggered explosives under the vehicle by remote control.

Later, another bomb attached to a police car was discovered close by. Residents were vacated, and the bomb was destroyed in a controlled explosion.

The initial attack prompted authorities briefly to seal air- and sea exits from the island, in a bid to prevent suspects from fleeing. However, Palma de Mallorca airport, Spain's third busiest, was re-opened within two hours.

The European Union condemned the attack as "barbaric". A statement released by the EU's executive also reaffirmed the bloc's support for Spain in its "fight against terrorism."

Violence mounts ahead of ETA anniversary

Thursday's violence comes on the heels of a similar bombing on Wednesday, and one day ahead of the 50th anniversary of ETA's founding, though the group has not claimed responsibility for the attacks.

Early on Wednesday morning, a car-bomb attack on a police barracks in Burgos in northern Spain injured around 60 people and caused extensive damage to the building and its surrounds.

Police said there was no telephone warning ahead of the attack, unlike many ETA bombings in the past, and this contributed to the high number of casualties.

There were around 120 people in the barracks and surrounding buildings, many of them children, when the explosion occurred at 4am.

ETA often plants bombs in Spain during the tourist season as part of its campaign to gain a separate homeland in the Basque region, which straddles parts of northern Spain and southern France.

On Friday, the group marks fifty years since the day it secretly formed to fight for Basque self-determination under the then repressive regime of General Francisco Franco.

Since first resorting to violence in the sixties, the group is accused of killing over 800 people.

Although polls indicate that most Basque's are in favor of greater separation from Spain, support for ETA's violence has waned in recent years.

The last fatal attack attributed to ETA was in June, when a booby-trapped car killed an anti-terrorist police officer in the Basque city of Bilbao.

Peace talks with the government broke down in December 2006 following a car bomb attack in Madrid.

nw/AP/Reuters/AFP
Editor: Neil King