A bomb placed under a police car killed two officers on the Spanish holiday island of Mallorca on Thursday, in what authorities called the second major attack by the Basque separatist rebel group ETA in two days, Reuters reported.
The bomb exploded outside offices run by the Civil Guard paramilitary police in Palmanova, a few kilometers (miles) from the Marivent palace where members of Spain's royal family were spending their traditional summer holiday, at about 1:50 p.m. (1150 GMT).
Police later deactivated another bomb placed beneath a second car near the site of the first explosion, an officer at the scene said.
Authorities briefly closed all ports and airports on the island to prevent the bombers' escape, a move the government called "Operation Cage" in a news release. German airline Air Berlin said 27 of its flights were delayed by the move.
Security forces believe ETA, weakened by arrests of top leaders, and long relatively dormant, is trying to put on a show of force to prove it is still able to strike at the Spanish state and to maintain morale among its supporters.
Officials were quick to blame the Basque rebels for the Mallorca attack, which came one day after 46 people, including sleeping children, were injured by a pre-dawn bomb aimed at family quarters of Civil Guard officers in the cathedral city of Burgos.
There was no immediate confirmation of local media reports that several other people were injured by the blast.
The Spanish government's representative on the island called ETA a "bunch of crazy murderers." Prime Minister Jose Luis Rodriguez Zapatero said the attack came as ETA was under more pressure than ever from security forces and promised the bombers would pay for their crime.
"They aren't going to escape justice. They're going to spend their lives in jail," Zapatero told a news conference.
On Friday ETA, blamed for more than 800 deaths over several decades, celebrates the 50th anniversary of its secret foundation during the Franco dictatorship when Basque culture was repressed.
The date will be cause for celebration for the minority of Basque nationalists who share ETA's policy of using violence to win independence for the Basque Country from the rest of Spain.
While polls indicate most Basques seem to favor some sort of independence for their mountainous region, which already has considerable autonomy, support for violence has slipped 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.
The Socialist government broke off peace talks with ETA after the rebels killed two people with a car bomb at Madrid airport in December 2006.