An explosion on a bus in central China's Hunan province on Sunday evening has left eight people dead and another 19 injured, state media said.

Eight people died at the scene of the blast in Guiyang County and at least seven of the 19 injured were in a critical condition, emergency workers said, according to China's official Xinhua news agency.

More than 200 police had been deployed to help rescue the injured and to divert traffic around the blast site, Xinhua said.

An investigation was under way, the report said.