Insurgents fired mortars at three areas where Ethiopian troops hold strategic positions in Somalia's capital on Thursday, leaving at least four civilians dead, witnesses said. One mortar fell near Mogadishu's Bakara market, killing three civilians and wounding five others, said Abdi Haji Nuur, who owns a spare-parts shop in the area. Nearby Ethiopian troops returned fire with artillery, witnesses said. At the sea port, where Ethiopian troops are living, a mortar fell on the beach near to where a group of children were swimming, killing one and wounding six, traditional elder Muridi Mayow said as he was taking the children to the hospital. "The children were hit as they were swimming. They are from the other parts of the city so we do not know their identity," he said. Three mortars also fell in the city's Hodan district, wounding six people in a residential area, witnesses said. The shelling follows two days of calm in Mogadishu, where Ethiopian troops have been protecting the weak transitional government as it attempts to assert its authority in the capital. An African Union peacekeeping force has been proposed to replace the Ethiopian soldiers, who are widely despised by Mogadishu residents. It was not clear, however, if the peacekeepers would be more welcome. Somalis held weekend demonstrations opposing the AU deployment. The Popular Resistance Movement in the Land of the Two Migrations has claimed responsibility for the attacks on government and Ethiopian forces in Mogadishu. The group has demanded the immediate withdrawal of Ethiopian forces.