Zhang Fucheng, an official in charge of rescue efforts, told Chinese television that efforts were being impeded by dense gas and collapsed tunnels.

The mine is located near the border with Russia, about 400km northeast of Harbin, the provincial capital.

Deadliest mines

It is run by one of China's top 520 state-owned enterprises, according to the website of its owner, the Hegang branch of the Heilongjiang Longmei Holding Mining Group.

It says the Hegang branch has more than 88,000 employees.

About 389 miners managed to escape after the gas explosion, Xinhua said, quoting officials at the mine.

China's mines are the world's deadliest, with safety standards often ignored in the quest for profits and the drive to meet surging demand for coal - the source of about 70 per cent of China's energy.

Official figures show that more than 3,200 workers died in collieries last year, but independent labour groups say the actual figure could be much higher.

Unregulated operations account for almost 80 per cent of the country's 16,000 mines.

The closing of many small, dangerous mines halved the average number of miners killed to about six a day in the first half of this year, according to the government.