A CAR BOMB has exploded 30 minutes ago in Madrid:

A strong explosion has been reported on near a convention center on the outskirts of the Spanish capital, Madrid.

Eyewitnesses told CNN ambulances had rushed to the scene following the explosion.

CNN's Madrid Bureau Chief Al Goodman reported that members of the Spanish royal family were expected later in the day at an arts fair at the convention center, which is in a residential area and near Madrid's airport.

The newspaper El Pais said on its Web site a destroyed car was seen at the site of the explosion, Reuters reported. The newspaper El Mundo said there were light injuries, the news agency added.

Radio and TV networks are reporting 11 slightly injured people; the area had been cordoned off before the blast, after someone claiming to be from ETA called the Basque newspaper Gara alerting of the forthcoming explosion.

UPDATE. A witness is on the radio at the moment, reporting that the police is now cordining off another area surrounding another convention center, the old one, in the Paseo de la Castellana, in the very heart of Madrid's financial district. Too soon to know whether it's a false alarm or it comes after a second phone call alerting of another blast.

UPDATE II. A police spokesman says that the second was a false alarm, and the cordon has been lifted.