A police officer and three Arab suspects were killed in an explosion in a Madrid suburb where police were hunting for suspects in the March 11th bombings. Eleven policemen were also reported to have been injured in the blast.
An Interior Ministry source earlier today confirmed an operation was under way in the suburb of Leganes linked to the investigation into the train bombings that killed 191 people, but declined to provide further details.
Low-flying helicopters scanned the area with searchlights and told residents to remain indoors. Others were evacuated.
Spain has charged 15 people over the bombings on four commuter trains, Spain's worst terror attack. The government has said its investigation is focused on the Moroccan Islamic Combatant Group, which has ties to the al-Qaida network.
Six are charged with mass murder, and nine are accused of collaborating with or belonging to a terrorist organisation. Eleven of the 15 charged are Moroccan.