An explosion shook an area near the airport used by low-cost airline Ryanair in the Spanish city of Zaragoza today following a warning call in the name of armed Basque separatist group ETA, officials said.
Police found three rocket launchers outside the airport, two of them empty. A third contained a grenade, a government spokesman in Zaragoza said. No one was injured.
Authorities evacuated the nearly empty airport before the blast, the spokesman said.
Witnesses reported hearing two whistling noises that sounded like rockets being fired, but there was only one explosion, the spokesman said. He declined to comment on media reports that an unexploded grenade was found near the airport.
The blast followed a warning call in the name of ETA to the Basque newspaper Gara, the newspaper said.
Zaragoza is some 250 km (150 miles) northeast of Madrid, about half the way to Barcelona.
A Ryanair flight due to land in Zaragoza at 1115 GMT was offered the option of landing at a Zaragoza military base or being diverted to another airport, the spokesman said.
The attack is the latest in a string linked to ETA since the Spanish government said last month it was open to negotiations with ETA if it laid down its arms and renounced violence.
None of the attacks, including a car bomb in Madrid, caused serious injury.
Spain's Socialist Prime Minister Jose Luis Rodriguez Zapatero has been forced to defend his offer since it won endorsement from parliament last month.
Many people and politicians on the right consider it a betrayal of ETA's victims and an unworthy concession to a group that has killed 850 people since 1968.
Hundreds of thousands of Spaniards demonstrated in Madrid on Saturday, calling on Zapatero to rescind the offer.
ETA has not killed anyone in more than two years amid a sustained police crackdown.
Zapatero said 178 ETA suspects have been jailed since he took office 14 months ago.