The crisis engulfing Yemen deepened on Wednesday with dozens of people killed as President Ali Abdullah Saleh reinforced his troops after heavy clashes with gunmen loyal to an influential tribal leader.
Overnight street battles left at least 41 people dead, some trapped in burning buildings. Fighting raged until dawn as presidential guard units shelled the headquarters of an army brigade responsible for protecting government institutions.
Arab embassies were said to be evacuating their staff and the few remaining western residents were being advised to leave urgently. The Foreign Office is urging all Britons to leave while flights are still available in a situation diplomats described as "worse than Libya."
Residents of Sana'a woke to a chorus of birdsong and machinegun fire as plumes of smoke rose into the sky, mortar blasts rattling windows and nerves. Heavy clashes resumed as Saleh's republican guard forces equipped with heavy artillery pushed the tribesmen out of government buildings. By nightfall they had wrested back control of several key positions.
The week's gun battles between rebel tribesmen and Saleh's troops have already claimed 200 lives and the confrontations are fanning fears of civil war.
Diplomats are fleeing the capital because of increasing violence. The violence is likely to spill over to the territorial waters making the transit around the Horn of Africa into the Red Sea more dangerous. Piracy is a significant concern.
It also provides an opportunity for al Qaeda to renew its efforts on the Arabian peninsula where it got its start.