A bomb exploded in the car park of a Madrid sports stadium that is the centrepiece of the city?s 2012 Olympics bid after a warning in the name of Basque guerrillas ETA, the Spanish government said on Saturday. There were no injuries, a government statement said.

The explosion came less that two weeks before the decision is announced on which city will stage the 2012 Olympics. ETA announced last weekend it would no longer target elected politicians, but the move fell short of the government?s call for a truce before it would start talks on prisioners and arms decommissioning.

The explosion followed a warning call in the name of ETA to Basque language newspaper Gara. Police had enough time to clear the area, where labourers are working to upgrade the stadium, the government said.

The bomb came on the same day as the Basque region?s nationalist premier, Juan Jose Ibarretxe, was sworn in for a new term. Ibarretxe has sought near independence for the northern Basque region from Spain.

ETA, classed as a terrorist group by the European Union and the United States, has killed nearly 850 people since 1968 in a bombing and shooting campaign for an independent Basque state in northern Spain and southwestern France.

ETA stages regular bombings but no one has died in an ETA attack since May 30, 2003, when a bomb killed two police officers and seriously injured a third in northern Spain.