Three men were shot in the south Mogadishu neighbourhood of Bulo Hubey early on Wednesday.
"Early this morning two men armed with pistols shot three men in civilian dress around Bulo Hubey. Two of them were dead and the third one was in serious condition, a witness, who asked not to be named, said.
"The victims were government employees."
Dahir Dheere, a medical officer at a Mogadishu hospital, said: "We received one person who has serious bullet wound on the head and his condition is grim."
Meanwhile, two civilians died and nine were wounded after a landmine exploded in the southern port city of Kismayu.
"Unknown gunmen remotely detonated a landmine when my car was passing at Alanley neighbourhood," a security agent told Reuters news agency.
"My bodyguards, driver and I survived, but the gunmen opened fire at us after the blast and my bodyguards defended me."
Witnesses said the blast killed two people.
"They were cut to pieces," Fadumo Abdulahi Hirse, a local resident, said.
Police station attacked
Late on Tuesday, fighters opposed to the interim government carried out one of their heaviest assaults on a police station near Mogadishu's Bakara market, Abdiwahid Mohamed Hussein, the police spokesman, said.
"Around seven in the evening, insurgents assailed Hawlwadag police station, firing rocket-propelled grenades and machineguns," he told Reuters by telephone.
"The police fought them and killed two of the insurgents while seriously wounding one. He was rushed to Medina hospital, but he died before reaching the hospital."
Somalia has been without a functioning government since the fall of Mohamed Siad Barre in 1991.
But violence has worsened since government forces, along with their Ethiopian allies, forced the Islamic Courts Union from Mogadishu in December last year.