Two employees of Medecins Sans Frontieres (MSF) have been kidnapped by gunmen in central Somalia.

The BBC's Somali Service says the two men, who work for MSF-Belgium, were taken in their car with their Somali bodyguards in Hudur, Bakol region.

The BBC's Mohammed Moalimo in Mogadishu says the area is run by the radical Islamist al-Shabab insurgent group.

A spokesman for MSF confirmed one Belgian and one Dutch aid worker were missing, but did not give more details.

"When we lose contact with teams we can't give much information because it can give problems afterwards, Michel Peremans said.

"I hope you can understand that this is too delicate, too problematic at this stage."

News agencies quoted witnesses and local clan elders as saying the two aid workers were kidnapped.

Unnamed humanitarian sources also said the aid workers had been abducted. The pair had been carrying out a nutrition study in Rabdhure, Reuters news agency reported.

The UN estimates 35 aid staff were killed last year and 26 abducted in the Horn of Africa nation, which has not had a functioning government since 1991.

The dead included three MSF workers - a Kenyan doctor, a French logistician, and a Somali driver - caught in a roadside bomb in the town of Kismayo in January 2008.

Al-Shabab has sworn to topple Somalia's fragile federal transitional government, which is backed by African Union peacekeepers in Mogadishu.