A car bomb placed by Basque terrorist group ETA exploded yesterday morning next to Madrid's main convention center, the IFEMA, causing minor injuries to 42 people.

The attack occurred near the pavilion where the Spanish monarchs and Mexican President Vicente Fox were set that afternoon to inaugurate ARCO, the country's largest art fair. Despite the blast, the opening ceremony went ahead scheduled.

Loaded with 30 kilograms of explosives, the car was parked next to one of the gates of the IFEMA Convention Center, in one of the city's main business hubs. The blast went off half an hour after Basque newspaper Gara received a warning call in ETA's name announcing that a bomb would soon explode in the IFEMA area.

This gave police enough time to cordon off the area and prevent further damage at a time when many people arrive at their offices. Six police officers and 34 employees in a nearby office building, belonging to the French technology company Bull, suffered minor cuts and wounds, mostly caused by flying debris and broken glass. Of those, 24 required hospital treatment, but were all released before the end of the day.

Terrorism experts are currently searching for two men who are believed to have left Madrid before the blast. The car they used, reportedly a Renault 19 with fake license plates, had been stolen some 12 hours earlier in Guadalajara, an hour's drive away from Madrid.

Prime Minister José Luis Rodríguez Zapatero, speaking at a press conference in Poland, condemned the attack and told ETA that there is no place for terrorism in politics. "Bombs only lead to prison," Zapatero said, adding that the Basque Country will build its future within Spain in spite of the terrorists.

All other political forces except the outlawed Batasuna - ETA's political wing - condemned the attack, the most serious bomb blast in Madrid since the March 11 train attacks.

Popular Party second-in-command, Ángel Acebes, highlighted that these are not times for "dialogue or truces," and called on the Basque government to respect "democratic decency" by helping authorities prevent Batasuna from running in the upcoming regional elections.

Batasuna, which was outlawed in March 2003 for failing to condemn ETA's acts of violence, refused to censure Wednesday's attack. "The politics of condemnation are politics of the past," Batasuna leader Joseba Permach said yesterday.

According to Permach, the explosion "illustrates the existence of a political and armed conflict between Euskal Herria [the Basque nation, encompassing the Basque Country, Navarre and three French provinces] and the Spanish and French states."

The blast coincided with a major overnight police operation against ETA’s recruitment apparatus across Spain.

Official sources say police arrested 14 people in the early hours of Wednesday morning. The arrests took place in the Basque Country, Navarre, Valencia and Cádiz, and, according to police sources, represented the “complete dismantling” of ETA’s recruitment apparatus.

The 14 people arrested had allegedly collaborated directly with ETA, offering the group logistic support. None of them had criminal records.

Despite the success of this operation, the IFEMA blast has cast a shadow over Madrid’s 2012 Olympic bid. The Convention Center is one of the main sites set to host sporting events in the city’s Olympic project, and security remains one of the key factors that will determine the International Olympic Committee’s final choice.

Wednesday’s blast was caused by the first ETA car bomb to explode in the Spanish capital in three years. In December last year, the terrorist group placed five small explosive devices in different petrol stations around the city, managing to paralyze traffic on Madrid’s major beltway on a bank holiday weekend.