Barcelona's metro is alleged to have been the target

Eleven suspected Islamist extremists have gone on trial in Spain, charged with involvement in a plot to stage suicide attacks on the Barcelona metro.

Prosecutors allege the defendants, nine Pakistanis and two Indians, were acting on orders from the Pakistan Taliban.

They are charged with belonging to a terrorist organisation, possessing explosive substances and falsifying official documents.

The accused deny the charges. The case is expected to last several weeks.

Prosecutors allege the group, who are appearing at the National Court in Madrid, were motivated by their opposition to the presence of Spanish troops serving with international forces in Afghanistan.

Spanish police uncovered the alleged plan after carrying out raids in Barcelona in January 2008.

Investigators said they decided to act after a member of the group warned the authorities.