Spanish police said Monday they aren't sure whether the armed Basque group ETA still has a unit on Mallorca following its planting of at least 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," said Regional Interior Ministry representative Ramon Socias.

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 during talks with police chiefs on the island.

Two bombs exploded Sunday in the women's restrooms in a bar and in an underground shopping area in Palma de Mallorca. Police defused a third bomb that was left in another city bar but did not explode.

Socias' office later said police were investigating whether a small explosion at another Mallorca bar represented a fourth bomb. That blast Sunday was initially ruled a gas explosion. The bar was closed at the time.

A taxi company in mainland Spain received telephoned warnings in the name of ETA before the explosions.

Authorities believe the latest bombings 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.

German Ambassador to Spain Wolf-Ruthart Born told SER radio that German tourists should exercise caution when traveling in Spain — but should keep coming.

"Spain continues to be the prime tourism destination for Germans despite everything and Germans want to continue coming to Mallorca," he said. "If the king is in Mallorca, then Germans can obviously come too."

The German Travel Association and Air Berlin, a major operator of flights from Germany to Mallorca, said they were not experiencing any dropoff in bookings or increased cancelations following the bombs.

The blasts coincided with the publication Sunday of an ETA statement in the Basque newspaper Gara.

The group claimed responsibility for recent attacks that killed three people and wounded 60, including the July 30 bombing in Mallorca that killed two police officers. The attacks appeared timed to the 50th anniversary of ETA's foundation 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.