The helicopter had been flying commanders of the rebel Liberty and Justice Movement (LJM) to Nyala in Darfur so they could travel on to Doha, where they were to attend peace talks between the Khartoum government and its opponents.

But bad weather Monday forced the chopper, which belonged to the Russian air company UTair and was carrying a four-member Russian crew, to land suddenly in an area where they were not expected.

Caught by surprise, Sudanese security forces detained the aircraft until its status could be clarified.

Nesirky said the three LJM commanders and the pilot were beaten at the scene and all those aboard the plane except the pilot were taken to a government military camp overnight before being sent to Nyala Tuesday.

“The pilot is still unaccounted for. The United Nations remains deeply concerned about his welfare,” Nesirky said, adding that UN officials were in close touch with Khartoum to try to locate him.

On Tuesday, Russian officials suggested that Darfur rebels seized the Russian helicopter.

But UTair later announced that the chopper had returned safely to base in Nyala “with its crew.”

And spokesmen for the two main Darfur rebel groups — the Justice and Equality Movement and the Sudan Liberation Army — said they knew nothing about a helicopter being seized.

The strife-torn western Sudanese region has seen a wave of kidnappings since March 2009, with 17 foreigners, including 10 Westerners, seized there.

Two German aid workers kidnapped on June 22 were freed on Tuesday.

Darfur has been gripped by civil war since 2003, which has left 300,000 people dead and 2.7 million displaced, according to the United Nations. Khartoum says 10,000 have been killed.