A car bomb exploded in a parking facility of Madrid's international airport, destroying or damaging more than 100 cars. This is the fourth attack against Spain's $60 billion a year tourist industry.

An anonymous phone call made to the traffic control service of the Basque Country in northern Spain alerted police in Madrid to the presence of a car bomb in a parking facility at Madrid's Barajas airport.

The caller claimed to speak in the name of the violent Basque separatist group, ETA.

Security agents were able to cordon off the parking garage so that there were no injuries when the bomb exploded. The blast ripped open a 35-meter-wide crater in one of the floors of the multi-story parking area setting 20 to 30 nearby cars on fire and damaging more than 100.

On July 26, anti-bomb specialists deactivated a car bomb placed in Málaga's airport, gateway to the famed Costa del Sol beach resorts. In mid-August, two bombs exploded on the tracks of the high-speed train line connecting Madrid to Seville. Three days later, a car bomb exploded outside a hotel in the coastal resort town of Salou south of Barcelona.

Last week, police in the Basque Country and in the northeastern autonomous Catalonia region arrested more than a dozen suspected ETA members. Authorities seized weapons and more than 400 kilograms of explosives. Police believe the blast at the Madrid airport was ETA's response to the arrests.

ETA has been waging a campaign for an independent Basque state in northern Spain and southern France, during which more than 800 people have died.