HOHHOT, April 30 -- Hundreds of firefighters are battling a fire that has engulfed a primeval forest in north China's Inner Mongolia Autonomous Region, according to local authorities.

The fire broke out at around 5 p.m. Sunday in the woods near the China-Russia border, in the northern Greater Hinggan Mountains.

Heavy smoke billowing from the dense woods impeded an airplane to check the situation.

The temperature in Inner Mongolia this spring is 1 to 2 degrees Celsius higher than in previous years, posing a higher fire risk for the region's primeval forests.