BBC's Frank Gardner in Dubai: Yemen promised co-operation

They want to interview 10 jailed Islamist extremists - three surviving kidnappers and seven alleged to be involved in a plot to blow up the British consulate in Aden last month.

The British investigators have asked the governor of Aden for permission to visit the scene of last week's fatal shoot-out, which left four of the tourists dead and two others injured.

They are looking for clues as to how the shooting began. The British Government is continuing to press the Yemeni authorities to justify their use of force in releasing the hostages.

The Yemeni Government says the kidnappers belong to a small, militant Islamic group called Jihad.

Security sources in the Yemeni capital, Sanaa, are quoted as saying the kidnappers had wanted to exchange the hostages for the suspected bomb plotters.

There has been no independent confirmation of any plan to blow up the Consulate. The BBC's foreign affairs correspondent says allegations of a militant cell working in Yemen might be a smoke screen to cover the government's botched handling of the kidnap. Britain has said it was not told about the plot until six days later.

The British Foreign Office has declined to comment on the alleged plot. Our correspondent says London may be keen to play down suggestions that British diplomatic premises abroad are at risk from retaliatory action for British participation with the US in the air attacks on Iraq last month.

Britain has warned its 300 nationals resident in Yemen to be extra-vigilant while it has advised all British tourists to leave.

Yemen and the Commonwealth

For its part, Yemen has said it no longer wants to join the British Commonwealth.

Although membership offers are the sole responsibility of the Commonwealth Secretariat, a Foreign Office minister told a Sunday newspaper that Yemen might not meet the membership criteria, which include what the Secretariat deems good government.

Britain ruled Aden between 1839 and 1967. Yemeni membership was put on the agenda at the 1997 Commonwealth summit.