Officials say they have boosted security at the Golden Gate Bridge in San Francisco, California, after videos of it and other US landmarks were seized from an al-Qaeda suspect in Spain.

Security has also been increased at Disneyland and at the Universal Studios theme park - two other California sites featured in the video tapes seized in three arrests on Tuesday.

"We're just taking it very significantly because of where it comes from," said George Vinson, the security advisor for California Governor Gray Davis.

The Statue of Liberty was among the landmarks in the video

Spanish authorities said the video tapes, which included pre-attack footage of the World Trade Center in New York from multiple angles, were too detailed to be a tourist's record.

And "substantial attention" in the videos is given to a Golden Gate Bridge suspension pillar, the authorities said.

Footage of the Sears Tower in Chicago, the Brooklyn Bridge, the Statue of Liberty and the Empire State Building was also found - all shot during a 1997 trip.

"Extremely violent" videos depicting terrorist training were seized as well.

The three men arrested in Spain were all Syrians, although two were dual nationals who also had Spanish citizenship.

They were identified as Ghasoub Al-Abrash Ghalyoun, Abdalrahman Alarnaot Abu-Aljer and Mohamen Khair Al Saqq. The video tapes belonged to Mr Ghalyoun, authorities said.

Mr Ghalyoun and Mr Abu-Aljer, arrested in Madrid, have Spanish citizenship. Mr Al Saqq was arrested in the eastern city of Castellon. Mr Ghalyoun had been previously arrested in April, and it was unclear why he was then allowed to free.

Operation Date

Although security was increased at the California locations seen in the videos, spokespeople at the other US landmarks in the tapes said they remained in the same higher state of alert they have been observing since 11 September.

The arrests were ordered by Spanish judge Balthazar Garcon as part of Operation Date, a counter-terrorism investigation by Spanish police that aims to dismantle Islamic terrorist networks in Spain.

At a press conference on Tuesday, Interior Minister Angel Acebes said that one of the suspects arrested belongs to the organisation the Muslim Brothers, a group linked directly to the financial activities of al-Qaeda.

Spain has been at the forefront of Europe's clamp-down on terrorism, not least because of its own problem with attacks from the Basque separatist group ETA.