Unidentified gunmen kidnapped two Somali employees of the U.N.'s World Food Program on Sunday, a Mogadishu-based member of the organization said, bringing to 20 the number of humanitarian workers kidnapped this year.
The two were conducting a nutritional survey between Jowhar and Balad, their colleague said, asking for anonymity because he was not authorized to speak to the media.
Nairobi-based spokesman Peter Smerdon confirmed WFP was investigating the whereabouts of two missing employees.
No group has claimed responsibility for the rash of kidnappings this year, or the dozen aid workers who have been killed.
Earlier on Sunday, Islamist fighters killed a Ugandan peacekeeper and wounded two others in the capital, a spokesman for the African Union force said.
It was the latest in a series of attacks by the strengthening insurgency over the Muslim holy month of Ramadan.
Barigye Bahoku said troops were fired on from the rooftop of an apartment building during a routine patrol near the airport.
"The attackers managed to escape because our troops reacted very professionally and did not fire back at the buildings where there were known to be civilians," he said.
The military wing of the Council of Islamic Courts, al-Shabab, claimed responsibility for the attack in a statement posted on an Islamic web site, Kataaib.
The African Union does not release reliable statistics on the number of peacekeeper deaths in Somalia. There are 1,800 Ugandan troops among the African Union forces in Somalia, where they help guard key buildings and the Mogadishu port, where food aid is unloaded.
In a separate incident, two Somali government soldiers were shot as they were carrying out a weapons search operation in Mogadishu's southern Hodan district, said witness Haji Ahmed Dahir.
Ethiopian troops supporting shaky Somali government forces have been battling an insurgency since they drove the Islamists from the capital and much of the south in December 2006.
Recently, Islamic fighters have regrouped to launch a series of hit and run raids on Somali towns. Last month they captured Kismayo, the third-largest city.
Somalia has not had a functioning government since a group of clan-based warlords overthrew a socialist dictator in 1991 and then fought each other for power.