An explosion near a police station on a Spanish resort island killed two officers today, a day after a car bombing blamed on Basque separatists injured scores in northern Spain, officials said.
The cause of the blast in Mallorca was under investigation and a Civil Guard spokesman in Madrid could not confirm news reports saying the explosion may have been caused by a bomb attached to the underside of a police patrol vehicle.
Planes and ships were blocked from leaving the island in the hunt for the bombers.
If confirmed as an ETA attack, it would conflict with government assertions that the group is seriously weakened after major police crackdowns in Spain and France in recent months.
The 50th anniversary of ETA's founding is Friday and the group may be trying to demonstrate with attacks on the two consecutive days before the milestone that it was not in any danger of breaking up.
The attack occurred in the Palmanova beach area, southwest of the island's capital, Palma de Mallorca.
The victims belonged to the paramilitary Civil Guard, which is chiefly in charge of policing rural areas and guarding official buildings. Mallorca is one of Spain's top tourist destinations and the explosion occurred at the height of the summer holiday season.
Spanish National radio said the blast shortly before 2 p.m. (1200 GMT, 8 a.m. EDT) was caused by a bomb attached to a Civil Guard jeep and that there were also several people injured.
Two officers were killed, the spokesman said on condition of anonymity in line with police department regulations. He gave no further details.
King Juan Carlos is vacationing on the island, but there was no indication he was the target or anywhere near the explosion. In 1995, Spanish authorities thwarted a plot to shoot the king with a long-range rifle while he was on vacation in Mallorca.
Wednesday's car bomb attack destroyed a police barracks in the northern city of Burgos and injured about 60 people.
That attack was blamed on the armed Basque separatist group ETA, along with seven other attacks this year.
ETA has killed more than 825 people since it launched a campaign in 1968 for an independent homeland in Basque region of northern Spain.
ETA did not phone in a warning before the Burgos attack as it typically does before most attacks, so authorities had no time to evacuate the 14-story building.
There were around 120 people in the barracks and surrounding buildings, a third of them children, at the time of the early morning blast.
The interior minister said the van had false license plates and had probably been stolen in France.
Spain has vowed to crush the separatist group since ETA ended what it had said was a permanent cease-fire with a massive bombing at Madrid airport in 2006.