The BBC has expressed growing concern at the detention in Yemen of three of its journalists, who've been held for nearly a week accused of unauthorised filming.

The BBC said the three Robin Barnwell, Rageh Omaar and Frank Smith were working in Yemen with the appropriate accreditation and were engaged in legitimate journalism.

It urged the authorities to allow them to return to Britain immediately.

A Foreign Office spokesman said Britain would maintain pressure at the highest levels until the journalists were freed.

They were detained after filming in a remote part of Yemen where a British family was recently held hostage.