Kenya has closed its border with Somalia amid fears that members of the Islamic Courts Union would slip across the frontier.
The UN said thousands of refugees are also near the border, unable to seek safety in Kenya.
Ethiopia to withdraw
Ethiopia has said that it intends to withdraw its troops from Somalia as soon as possible - even though the weak Somali government depends on the Ethiopian army's tanks and fighter aircraft.
|The Somali government says it wants to rebuild the war-ravaged country[AFP]|
Jendayi Frazer, the assistant US secretary of state for Africa, however said on Thursday that Yoweri Museveni, the Ugandan president, had promised George Bush, the US president, that he could supply between 1,000-2,000 troops to protect Somalia's transitional government and train its troops.
"We hope to have the Ugandans deployed before the end of the January," Frazer told journalists after meeting with Museveni in the Ethiopian capital on Thursday.
A three-day amnesty for Somalis to give up their weapons expired on Thursday although few residents of Mogadishu had apparently given up their guns by the end of the day.
Throughout the amnesty period, the city's Bakaara arms market continued to do brisk business in Kalashnikov rifles and machine guns.
But Ali Muhammad Gedi, the Somali prime minister, said the disarmament programme was working, and that his forces would seize large arms caches located around Mogadishu this week.
He said a house-by-house search would follow, without offering a timeline.
Somalia's last effective central government fell in 1991, when clan-based warlords overthrew Mohammad Siad Barre and then turned on each other.
The current government was formed two years ago with the help of the United Nations, but has been weakened by internal rifts.