Javier and David Couso are joining an initiative by the Free Association of Lawyers that maintains that Aznar is breaking Spanish law by involving their country in a military conflict without authorisation from both houses of parliament and the King, who is head of state.

Despite fierce popular opposition, Aznar's conservative government has been one of the most vocal supporters of the US-led war in Iraq.

The brothers also wrote to the Spanish foreign ministry demanding information regarding the circumstances of their brother's death and what diplomatic steps have been taken to get Washington to explain the killing of their brother in the Palestine Hotel.

"We want to know if we live under the empire of law or under the law of empire," the brothers said at a press conference.

The Spanish government, as well as international media groups, have asked Washington to look into the deaths of two Spanish journalists: 37-year-old cameraman Couso and 32-year-old journalist Julio Anguita Parrado, who was killed on Monday by Iraqi rocket fire.

Meanwhile, the Spanish foreign ministry said on Friday that journalists should not leave Baghdad because of a lack of security.

On Wednesday, the defence minister had told Spanish journalists to leave the Iraqi capital as they might become militray objectives for Iraqi troops.

SPACE.WIRE