A van loaded with a bomb exploded Monday in the east of Madrid but no one was injured in the blast, national radio reported, citing police, AFP reported.
The explosion took place around 0800 GMT after a telephone warning to the Red Cross that gave police time to cordon off the area, the radio said.
No one has yet claimed responsibilty for the explosion, but the radio speculated that it could be the work of the armed Basque separatist group ETA three weeks ahead of regional elections in Spain's Basque region.