Officials in Somalia say two policemen have been gunned down in the capital, Mogadishu, as more African Union peacekeepers arrive.
Police and witnesses say the two officers were checking vehicles for weapons on a road leading to the airport when the attack occurred Wednesday. Officials say an investigation is under way to find the killers.
Meanwhile, additional AU troops have been arriving in Somalia from Uganda. Mortar shells struck the Mogadishu airport as the first 350 Ugandan troops flew in on Tuesday.
Somalia's transitional government has struggled to contain violence in the capital since its forces, along with Ethiopian troops, drove out a rival Islamist movement in December.
The Ugandan troops are the vanguard of an AU mission meant to stabilize the country.
The AU hopes to gather 8,000 troops in all, but member nations have so far pledged only half that number. The force will replace the Ethiopians, who Addis Ababa intends to gradually withdraw.
The insurgents in Somalia are believed to be a mix of defeated Islamists and clan leaders resisting the transitional government.
The Islamists have issued repeated warnings that they will attack any peacekeepers who set foot in Somalia.
Some information for this report was provided by AFP and AP.