Spanish authorities said they aren't sure whether the armed Basque group ETA still has a unit on Mallorca following its planting of three small bombs on the Mediterranean tourist island.

"We have to work on both hypotheses: that they are still here and that they may have quit the island," Regional Interior Ministry delegate Ramón Socias told the radio station Cadena SER.

He said police investigations should establish whether Sunday's small blasts were triggered by timers. In that case, the devices could have been planted days in advance and given the militants ample time to escape undetected.

The blasts, which caused no injuries and little damage, came barely a week after ETA killed two police officers in another bomb attack on Mallorca.

Police also are trying to establish if the same ETA unit was responsible for all the blasts.

King Juan Carlos, who is on the Spanish royal family's annual holiday on the island, denounced the attacks.

"That band of murderers and scoundrels will neither alter Spanish democratic life nor normality on the island," he said in talks with police chiefs on the island.

Sunday's bombs were planted in the toilets of a bar and a restaurant in Palma de Mallorca and in an underground passage at the central Plaza Mayor square. They were preceded by warning calls in the name of ETA to a taxi company on mainland Spain.

Authorities believe the explosions are aimed at striking fear among tourists at the height of the summer holiday season. In past years, ETA often has sought to harm the tourist industry by planting small bombs in resort areas.

Mallorca is one of Europe's main tourist destinations, particularly among Germans and Britons. In June, about 2.6 million passengers used Mallorca airport while more than 22 million passed through it last year.

"We condemn the attacks," German Ambassador to Spain Wolf-Ruthart Born told SER. "These atrocities are worthless and have no justification in a democratic country like this."

He said that although Germany had issued a warning to its travelers to be cautious, "Spain continues to be the prime tourism destination for Germans despite everything and Germans want to continue coming to Mallorca."

"If the king is in Mallorca, then Germans can obviously come too," he said.

The blasts coincided with the publication Sunday of an ETA statement in the Basque newspaper Gara, one of its usual mouthpieces.

The group claimed responsibility for recent attacks that killed three people and wounded 60, including one the July 30 bombing in Mallorca that killed two police officers. The attacks preceded the 50th anniversary of ETA's founding on July 31, 1959.

ETA has killed more than 825 people since 1968 when it began launching attacks in pursuit of an independent Basque state.

•Bomb explodes in Mallorca