Five other passengers were injured in the crash at about 10am, according to the UN spokesman Liam McDowall. A Foreign Office spokeswoman said last night that a British man was reportedly on board, but that his fate was not known.
The helicopter, a Ukrainian aircraft hired by the UN mission, took off from Sarajevo at about 9.15am. It was carrying senior officials in the UN mission and other international organisations to talks with local authorities in the town of Bugojno in Bosnia's Muslim-Croat Federation.
The Nato-led peace force said it had sent helicopters to the site of the crash in a mountainous region around Fojnica, about 50km (30 miles) northwest of the capital Sarajevo.
"The search and rescue operation is completed," Mr McDowall said.Reuse content