A British consultant working for Save the Children in Somalia was abducted by masked gunmen last night along with his native colleague, the aid agency said today.
The charity is calling for their immediate release.
Anna Ford, a spokesman for the aid agency, said: "Save the Children can confirm that a British national and a Somali national working with the agency were taken by armed gunmen on Thursday night from a guesthouse compound in Adado, a Somali town near the Ethiopian border.
"Save the Children was assessing the feasibility of starting up a humanitarian programme to help malnourished and sick children and their families in the area.
"We are extremely concerned about the welfare of those being held and urgently call upon whoever is holding them captive to release them unconditionally."
Local resident Moalim Bashir was unable to say who had taken the two men from the town of Adado, where tensions are currently high.
But he said militia massing to the south posed a threat and could try to take the town from those currently in control.
Several forces have gunmen in the area, including pirate gangs and factions of militias allied to the government.
A spokesman for the British Foreign Office said officials were "urgently investigating" the kidnapping.
Some reports this afternoon suggested the Somali national may have been released.
The stricken Horn of Africa nation has been beset by famine and years of fighting between rival warlords leading to thousands of deaths.
It has had no functioning central government for nearly 20 years.
But the western part of the country had been considered one of its safer areas.
Though most aid agencies have pulled out of the region, some had recently considered a return.
Save the Children has been working in Somalia for more than 40 years, with a focus on improving access to food, basic healthcare and education.
The charity is largely based in the central Hiran region, Karkaar in the north east and in the Togdheer region of Somaliland.
Its work has been limited by the security situation but this year it began to pool resources with two other branches of the International Save the Children Alliance - and Finland - to become a unified presence in the country.