UK nationals advised to leave Ivory Coast amid threat of violence

It said the threat of widespread instability and violence meant that anyone without a "pressing need" to remain should seek a safe way to get out by commercial means.

The escalation of the travel advice warning followed an attack on a United Nations base by six masked gunmen as Laurent Gbagbo continued to defy international calls for him to accept defeat in the poll.

Britain has urged all parties to respect the results announced by independent observers, and backed by the UN, which gave victory to opposition leader Alassane Ouattara. The presidential election was intended to restore stability to the country following a long-running civil war which began with a 2002 coup attempt against Mr Gbagbo, who has ruled since 2000 without facing election.

A meeting of the UN Security Council today is due to discuss the latest developments and the renewal of its mandate in the country, which is due to expire on December 31.

The European Union gave Mr Gbagbo until yesterday to give up power or face sanctions.

But he is now demanding that the 9,000 UN peacekeepers – some 800 of them guarding a compound from which Mr Ouattara is attempting to govern – leave.

As many as 30 people died in violent clashes on Thursday.

On its website, the Foreign Office said that: "In view of the tense and highly uncertain security environment following the disputed presidential election... we advise against all travel to Cote d'Ivoire.

"Due to the threat of widespread instability and violence in Abidjan and other major cities British nationals are advised to leave Cote d'Ivoire by commercial means, if safe to do so, unless you have a pressing reason to remain." Borders and airports could close again, it warned.

Any Britons who chose to remain "should maintain a high degree of vigilance, keep a low profile, avoid the area immediately near the Hotel Golf in Abidjan, be aware that roadblocks can be imposed without notice, keep several days' stock of food and water and stay indoors until any demonstration or rally in your locality has passed", it advised.

Mr Gbagbo's spokeswoman said the UN mission had not remained neutral in the election dispute and accused it of arming the New Forces rebels allied with Mr Ouattara. The United Nations certified results showing that Mr Ouattara had won by "an irrefutable margin".