HOHHOT, June 6 (Xinhua) -- A forest fire that lasted for five days in north China's Inner Mongolia Autonomous Region was put out Wednesday morning, local authorities said.

The fire started Friday in the Hanma National Nature Reserve in the northern area of the Greater Hinggan Mountains, and spread to neighboring Heilongjiang Province by Sunday afternoon. It was put out at around 10 a.m. Wednesday.

The fire has burnt around 5,100 hectares of forest, with 4,500 hectares in Inner Mongolia and 600 hectares in Heilongjiang, according to the fire department in the nature reserve.

Since Friday, thousands of armed police, forest police, militia and fire fighting forces have been dispatched to battle the fire.

Lightning strikes were the cause of the fire.