People have started fleeing the worst violence in months
Renewed fighting has broken out in the Somali capital, Mogadishu, with African Union peacekeepers coming under attack from Islamist insurgents.
At least 15 civilians have died since clashes erupted late on Tuesday and people are fleeing the city.
Insurgents attacked Ugandan peacekeepers, who responded with tank and artillery fire.
On Monday about 30 people were killed and dozens wounded in some of the worst violence Mogadishu has seen in months.
The BBC’s Mohammed Olad Hassan in Mogadishu says Islamist insurgents have been gaining ground in the city in their fight against the Ethiopian-backed government.
Observers say there has been a change in tactics, with Islamists switching from hit-and-run raids to sustained attacks against peacekeepers.
Tuesday’s clashes happened in the south of the city.
Our reporter says heavily armed insurgents attacked the AU base at K4 – a strategic junction in the south of the city linking the airport and the presidential palace.
Peacekeepers at the K4 base responded by firing into Bakara market, a scene of frequent fighting where most of the victims of Monday’s violence were killed.
A shell hit our house, my father was killed and his body is here
Peacekeepers mired in Somalia
The sounds of deafening gunfire and bombardments could be heard throughout the city overnight, he says.
It was the third sleepless night for residents and the second serious attack against AU peacekeepers in a week.
Peacekeepers have generally been considered friendly since their arrival last year, and residents have been upset by the scale of their retaliation, our reporter says.
Maj Bahoku Barigye, an spokesman for the African Union Mission to Somalia (Amisom), said the peacekeepers had not suffered any causalities nor had their moral been affected.
He denied that the attacks were getting worse.
« I have been here for about eight months and I have not seen any difference whatsoever, » he told the BBC’s Network Africa programme.
‘No lost cause’
But people living by the AU bases have started to flee their homes.
« A shell hit our house, my father was killed and his body is here, and I don’t know where anybody else is, » a distressed woman in the capital told the BBC’s Somali Service.
Local residents told AFP news agency that shelling killed four people in one house and three in another area.
Most of the AU peacekeepers in Somalia are from Uganda
Somalia has been wracked by conflict since 1991, when former President Mohamed Siad Barre was overthrown.
The Ethiopians intervened in 2006 to help the government oust Islamist forces from the capital and surrounding regions.
The Islamists then launched an insurgency against Somalia’s transitional government.
David Shinn, a former US diplomat who teaches at the George Washington University, said fighters from the hardline al-Shabab militia were trying to assert their authority in order to force the Ethiopians out.
They are trying « to show that they are in a position to perhaps even take control of Mogadishu if the Ethiopian forces were to leave », he told the BBC.
Maj Barigye said it was unrealistic to expect a quick resolution to Somalia’s long-running conflict.
« There is no lost cause here, » he said.
« It’s just a question of time, a question of patience, it’s a question of tolerance, it’s a question of understanding. »
Only Uganda and Burundi have contributed troops to the AU peacekeeping force, which has just 2,000 troops of the 8,000 planned.
But Mr Shinn said adding more peacekeepers would not help.
« The only way out of this mess at the moment is to have a successful negotiation between moderates and the Alliance for the Re-Liberation of Somalia, the ARS, and the transitional federal government, » he said.
The UN has been leading peace negotiations over Somalia in neighbouring Djibouti, but al-Shabab has so far rejected the process.
A ceasefire due to be signed at the end of last week has been delayed for another month.