Spain has said that two suspected members of Eta, the Basque separatist group, who were arrested on Sunday were behind the bombing of a Madrid airport car park in 2006.
Alfredo Perez Rubalcaba, the country's interior minister, said: "These are the people who caused the [December 2006] explosion which killed two people in Terminal Four."
News of the arrests comes as the Socialist government campaigns for general elections which will be held on March 9.
The government broke off peace talks with Eta after the car bomb wrecked a car park at the airport, killing two Ecuadorean immigrants who had gone to sleep in parked vehicles.
Hidden weapons
Martin Sarasola and Igor Portu were arrested in Spain's Basque region on Sunday and found to be carrying hidden weapons.
Portu was admitted to intensive care shortly afterwards, suffering from a broken rib and a punctured lung.
The government said he was hurt resisting arrest. On Tuesday, Spanish police announced that they had found 125kg of bomb-making material in a cache discovered after the arrest of the two men.
The discovery, made in the northern province of Huesca, also contained detonators and timers, an interior ministry spokesman said on condition of anonymity.
The hidden materials were traced after police found a sketch map on one of the two detainees.