Spanish police are examining a video which may have been made by Madrid bomb suspects minutes before they blew themselves up.
The bombers' alleged ringleader is said to deliver the video threat
The video, found in the rubble of the Madrid flat where seven suspects died last weekend, contains an al-Qaeda ultimatum to Spain.
Three men, believed to be among the dead, demand the immediate withdrawal of Spanish troops from "Muslim lands".
Reports on Friday said the video was made as police raided the flat.
Radio Cadena Ser quoted anti-terror experts as saying the front door of the flat could be seen buckling as Spanish police tried to force their way in.
A policeman died in the blast, last Saturday, along with the seven suspects. Some had already been named as key figures in the Madrid train bombings on 11 March, when more than 190 people died and 1,900 were injured.
The statement in the video was made in the name of a group calling itself the "al Mufti and Ansar al-Qaeda brigades".
The alleged bombing mastermind, Serhane ben Abdelmajid Fakhet, known as "the Tunisian", is said to be the man seen warning Spain to get its troops out of Iraq and Afghanistan.
Seven suspects and a policeman died in the blast
"Should you not do this within the space of a week,
starting today, we will continue our jihad (holy war) until
martyrdom," the statement added.
"You know that you are not safe, and you know that Bush
and his administration will bring only destruction. We will
kill you anywhere and in any manner."
Two Moroccans identified by the police as suspects in the
bombings, Jamal Ahmidan and Abdennabi Kounjaa, could also be seen on
the new tape, reports say.
An earlier letter had warned of an "inferno" if forces were not withdrawn.
Key Madrid suspects
Sarhane ben Abdelmajid Fakhet: Dead
Abdennabi Kounjaa: Dead
Jamal Ahmidan: Dead
Rachid Oulad Akcha: At large
Mohammed Oulad Akcha: At large
Said Berraj: At large
The video has been sent to the National Court as evidence.
Spain's incoming Socialist government, elected days after the train bombs, has said it will pull its forces out of Iraq by 30 June unless control is handed to the United Nations.
Three Spanish soldiers were injured, one seriously, in an ambush in Iraq late on Thursday. Eleven Spaniards have died in Iraq in the past year.
Seventeen people, including 13 Moroccans, have been
provisionally charged over the train bombings. Six are accused of mass murder and the rest
with collaborating or belonging to a terrorist group.
Some key suspects remain at large.
Spain is on high alert over the Easter holiday period after the Madrid attacks, a foiled attempt to blow up a railway line a week ago and reports that an attack on a Madrid leisure complex had been planned.
Police and soldiers are guarding dams, power
plants, high-speed rail lines and other possible targets.
"We're not resting easy - there could be another one," an
unnamed Interior Ministry official said.
Other European countries also remain on high alert amid fears of an Easter attack.