The three crew and 12 passengers on board the helicopter were killed when it crashed in fozest in western Siberia's Tyumen region, an emergencies ministry spokesman said.

"The helicopter started spinning around then fell to the ground and exploded," the spokesman told AFP, quoting a witness at the scene.

The stricken helicopter was lying on its side in flames some 90 km from the settlement of Raduzhnoye, the Interfax news agency said.

The helicopter was one of two on a mission to survey the region's dense forest, a spokeswoman said earlier.

Those on board the second helicopter had landed nearby and were attempting to help at the crash scene.

Meanwhile rescuers and medics were on their ay to the scene.

A commission has been set up to investigate the crash, ITAR-TASS news agency said.