BBC News with Mary Small.

The United States and Britain have closed their embassies in Yemen because of what officials say are continuing threats from al-Qaeda. The US embassy has told its citizens in Yemen to be vigilant. President Obama has accused a Yemen-based group linked to al-Qaeda of being behind a failed attempt to blow up an American airliner over Detroit on Christmas Day. Jonathan Head reports from Yemen.

The US Embassy in Sana'a resembles a fortress, guarded by heavy machine guns and a formidable row of concrete barriers. The British Embassy is more discreetly protected. Both, though, remain closed for the moment because of intelligence suggesting a terrorist attack is now far more likely. A recent statement by al-Qaeda in the Arabian Peninsula, the group blamed for the failed Christmas Day bombing, called for an all-out war against what it called the "crusaders who work in embassies".

A senior White House official has said that lapses and human errors were to blame for the American security service's failure to identify the Nigerian suspect, Umar Farouk Abdulmutallab, in advance over the attempted Detroit bombing. Imtiaz Tyab reports from Washington.

The White House counter-terrorism and security adviser John Brennan is leading a review ordered by President Obama of the alleged attempted bombing of the Northwest Airlines flight on Christmas Day. He said there were lapses and errors in the sharing of intelligence, but no single piece of evidence pointed to an attempted attack. US authorities have charged 23-year-old Nigerian Umar Farouk Abdulmutallab with trying to blow up a US-bound flight with explosives he had smuggled to board in his underwear.