MOGADISHU (AFP) - At least 23 people were killed in the Somali capital when fighters attacked camps housing African Union and Ethiopian troops on Thursday, triggering heavy clashes, witnesses and police said. The fighters shelled bases housing AU peacekeepers and Ethiopian troops in southern Mogadishu's K4, Shirkole and Hamarjadid quarters, drawing retaliatory fire. Somali forces joined the battle to support the peacekeepers, they said. Witnesses said several residents were also wounded in outlying districts in some of the heaviest fighting in Mogadishu, the epicentre of heavy clashes for nearly two decades. "I saw four civilians, one of them a woman, and an insurgent fighter killed in Taleh area. The civilians were caught in the crossfire," said witness Hasan Yahye. Colonel Farah Abdullahi, a Somali policeman, said two officers were killed in the clash between AU troops and insurgents. Sixteen other civilians died in fighting between Ethiopian troops and insurgents, bringing the death toll to 23. "Four civilians died and three others wounded when an artillery shell hit their house near a vegetable market in Bakara," Osmail Adan, a witness told AFP. Another witness Ali Muhammad Siyad reported five fatalities in a Bakara teashop. "I was drinking tea when a mortar struck, killing five people. There was smoke and shrapnel all over the teashop. I was very lucky not to die but I sustained small injuries," Siyad said. A family of three was killed when a mortar crashed into their house. "My father and my two sisters were killed by a mortar shell and their bodies are still lying in the house. I don't know what to say, its dark moment," said Shafici Ahmed. A man and woman were killed when a shell crashed into a telephone booth in Bakara. "It was terrible, I saw my friend die as a result of serious injuries caused by a mortar shell that destroyed his telephone booth. A woman also died after shrapnel cut her to pieces," said Ali Osman, a witness. Witness Sirad Nur Roble said two other civilians were killed elsewhere in Bakara, one of the most volatile zones in the battle-wracked seaside capital. Witnesses said the shells destroyed residential and business premises in Mogadishu, where hundreds of thousands of residents have fled the bloody duels for dominance in the recent months.