A week ago, British citizens were warned not to travel to the Middle Eastern state.

In view of the heightened threat of terrorism against Western interests in Yemen, we have decided to amend our travel advice - we now advise against all travel to Yemen; that all British nationals in Yemen should consider leaving

Foreign Office

On Friday night, the Foreign Office re-issued the warnings and amended its original advice by adding "all British nationals in Yemen should consider leaving".

The advice was posted on the department's website.

The government declined to go into details about the nature of the threat, or to say whether it was general or specific.

On 8 November, the Foreign Office only advised against "all non-essential travel" to Yemen.

Now it is urging the 300 Britons thought to be living in the country to leave.

Tanker attacked

On 6 October, a French oil tanker was damaged by a bomb off the coast of Yemen, and a Bulgarian sailor killed.

The bombing and a spate of other recent terror attacks in the Arab world and Asia were hailed in an audiotape attributed to al-Qaeda leader Osama Bin Laden and broadcast by Al-Jazeera television on Tuesday.

He also praised last month's Moscow hostage-taking and threatened US allies, including Britain.

Britons have been advised to be vigilant in Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates.

They have also been warned against travel to some areas of South East Asia - Indonesia being one of them, following last month's bomb blast in Bali.