Two UN workers, a Briton and a Frenchman, have been shot dead as they disembarked from a plane at an airport in Galkayo, central Somalia, officials and witnesses say.
United Nations sources confirmed the two men were international consultants with the United Nations Office on Drugs and Crime (UNODC).
An airport official said the attacker was dressed in a police uniform.
"One of them died inside the airport and the other one was rushed to hospital where he later died of the injuries. Both of them were white men," said witness Hassan Ahmed.
A spokesman for the British Foreign Office confirmed the incident in Galkayo, which is situated 575km north of the capital Mogadishu, and on the border with the northern breakaway state of Puntland.
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UN security in Galkayo, which is outside of effective central government control, is normally extremely tight.
The two men had reportedly flown into Galkayo to meet with Somali officials on the issue of regulating the money transfer services that replace a formal banking system in Somalia.
UN staff members have been regularly targeted in Somalia, where the fragile internationally-backed government backed by African Union troops is battling al-Qaeda-linked al-Shabab rebels.
In February, at least six people were killed in a suicide car bomb attack targeting a United Nations convoy close to Mogadishu's heavily-fortified international airport, among them four local security escorts working for the UN.
In June last year, al-Shabab rebels carried out a raid against a UN compound in Mogadishu, killing 11 people.
