A gas explosion at a coal mine in central China has killed 29 miners, according to state media, the latest in a series of deadly accidents to hit the country's mining industry.

Some 35 miners were working in the state-owned mine at the time of the blast, which happened early Saturday evening at the Xialiuchong Coal Mine in Hengyang city, Hunan province, the official Xinhua news agency said.

State television put the number of dead at 29, raising the toll of 28 earlier given by Xinhua. All the bodies of the dead had been recovered, China Central Television said.

Six miners had been rescued and were being treated in hospital. Relatives had earlier gathered outside the mine in the early hours of Sunday morning to await news of the missing miners, China News Service said.

The mine, which was owned by the city government, was legally registered, state television said. The mine had more than 500 employees but only 160 workers were on shift at the time of the accident.

The cause of the accident was still under investigation.

Government officials could not immediately be reached for comment.

The head of the central government's work safety agency, Luo Lin, and Hunan governor Xu Shousheng had travelled to the scene to help direct the rescue and recovery efforts.

China's mining industry has a notoriously poor safety record with its mines considered among the most deadly in the world.

Earlier in October, a gas explosion in a coal mine in China's southwestern city of Chongqing killed thirteen people, while another blast in the northern province of Shaanxi killed 11 miners.

In 2010, 2,433 people died in coal mine accidents in China, according to official statistics -- a rate of more than six workers per day.

Labour rights groups say the actual death toll is likely much higher, partly due to under-reporting of accidents as mine bosses seek to limit their economic losses and avoid punishment.

As China's rapid economic growth has caused demand for energy, including coal, to surge, some mining bosses have put the safety of workers at risk to chase profits.