US Secretary of State Hilary Clinton says Yemen's instability poses a threat for the region and the world. Mrs Clinton called on the international community to redouble its efforts to support the government in Sanaa.

The Yemeni authorities have stepped up security at embassies and the capital's airport. Several Western embassies have closed partially or completely. The Nigerian who tried to blow up a US airliner on Christmas Day was allegedly trained by al-Qaeda militants in Yemen. Shortly before the failed attack he stayed for several weeks in Ghana. FBI agents are now tracing his steps there.

Security surrounding the US embassy in Sanaa (Photo: ANP/EPA)