At least five people have been killed in the Somali capital, Mogadishu, when Islamist gunmen attacked a warlord, breaking a three-day truce.
UK minister Hilary Benn is in Baidoa to support the interim government
A compound belonging to warlord Mohamed Omar Habeb Dheere north of Mogadishu was overrun by the Islamist gunmen.
The attack coincided with a rally intended to call for peace, following the death of at least 140 people.
Hundreds of demonstrators chanted anti-US slogans, accusing the US of backing the alliance of warlords.
Reuters news agency reports that Mr Dheere had arrived from his base in Jowhar at the weekend to back up the warlords' Alliance for the Restoration of Peace and Counter-Terrorism.
SOMALIA'S THREE RIVAL GROUPS
Gets arms from: Ethiopia, Italy (Source: UN report)
Gets arms from: Eritrea (Source: UN report)
Anti-terror alliance of warlords
Believed to get support from US
The US says it has not violated the arms embargo on Somalia but has said it would work with those who can help "prevent Somalia becoming a safe haven for terrorists".
British international development minister Hilary Benn, who is in Somalia on a previously unannounced visit, said he was aware of allegations the US was funding warlords.
"I haven't seen any evidence myself," he said.
Reports suggest two of those warlords may soon be sacked from the interim government.
The government is based in the small town of Baidoa, three hours from the capital, Mogadishu.
It has not moved to Mogadishu because of security concerns, and controls only a small part of the country.
Mr Benn, who met the president and prime minister, says he will be offering international support for attempts to end the anarchy.
Somalia has not had an effective national authority for 15 years since the ousting of President Siad Barre in 1991.