Armed tribesmen have kidnapped four German tourists in Yemen.

The three women and a man were reported to be on their way back to the capital, San'aa, from a tour of central Yemen when their truck was stopped by the tribesmen.

Correspondents say they are the latest in a series of foreigners who have been held by Yemeni tribemen as bargaining chips in disputes with the government - most have been released unharmed after being treated as guests.