Islamist groups fighting government forces in the Somali capital have advanced close to the presidential palace in some of the worst clashes for months.
More than 100 civilians have died in the violence in Mogadishu in the past few days and 25,000 have reportedly fled.
Sources say the government's leadership is crumbling and many of its troops have defected to the rebels.
The BBC reports Mogadishu has seen plenty of fighting over the years but this appears to be on a different scale.
Indonesia has offered to spearhead United Nations peacekeeping in Somalia, but a UN official says a mission is too risky for now.
United Nations officials insist a Muslim country should be in charge of any UN force sent there.
