Thousands of fire fighters are fighting to extinguish more than 10 forest fires in North China's Shanxi province, fire control authorities said on Saturday.

A preliminary investigation showed that lightning was primarily responsible for most of the wildfires, according to a statement from the provincial forest fire control headquarters.

The headquarters has sent work teams to direct the firefighting operations, it said.

More than 3,300 people are battling the worst fire, which stretches 10 kilometers in a forest bordering the cities of Jingzhong and Yangquan.

Strong winds and the steep mountain hinder firefighting efforts, said a firefighter.

However, the local weather bureau predicted that the wind would weaken after 5 am on Sunday, which would make it easier for firefighters to battle the raging blaze.

The fire has engulfed largely uninhabited mountains of shrubs, wild grass and some stretches of Chinese pine trees. It currently poses no threat to densely populated villages or important facilities, according to an earlier statement from the headquarters.

No casualties have yet been reported.