At least 12 people have been killed in heavy shelling between Somali troops and anti-government fighters near the presidential palace in the capital, Mogadishu, witnesses have said.

The latest casualties came a day after 23 people were killed and 51 injured on Saturday in fighting between the two sides.

"It was a very gruesome scene," a local resident, who saw dead bodies and wounded people running away from the scene on Sunday, said.

Ali Adde, deputy-director of Madinah hospital in Mogadishu, said that they had received 31 patients with serious injuries.

"The hospital is over crowded with injured people," he said.

Somali forces and the anti-government fighters, who intend to install an Islamic state in Somalia, blamed each other for sparking the violence.

AU troops

More than 4,000 African Union peacekeepers are in Somalia, but they often come under attack and are ultimately confined to protecting key government institutions.

A surge of violence that erupted in Mogadishu in May has killed about 200 people and forced tens of thousands to flee the capital.

Somalia has been without an effective government since 1991 when the overthrow of the government at the time plunged the country into chaos.

A UN-backed government is currently in place in Mogadishu, but it is struggling to restore order with anti-government fighters controlling large patches of the country.