Earlier, in the southern Hodan district, one person died and four were injured when government forces opened fire after their vehicle was hit by a roadside bomb, sources said.
Five others were injured when a hand grenade was hurled at a police convoy carrying prisoners in the southern Huriwa quarter, said Ahmed Halane, a local resident.
"Some of the prisoners managed to escape but others were re-captured," he said.
Officials from the transitional government said they could not be deterred by the violence, as the reconciliation conference went into its third session on Saturday.
Critics have argued the meeting will have little effect as the Islamic Courts Union, which had controlled most of the country before being driven from out by Ethiopian and government forces earlier this year, is boycotting the proceedings.
The Islamic Courts, the leaders of which are exiled in neighbouring Eritrea, has said that any peace conference should be held outside Somalia.
Somalia has seen more than a dozen peace initiatives, with little success, since the 1991 overthrow of Siad Barre, the country's former president.
Amid the continuing violence, the African Union has extended its peacekeeping mission to the country.