An accident at the state-owned Soko coal mine in Serbia has killed at least eight people and injured at least 20.

The accident happened around 6 am local time, Serbian state television RTS said. Part of the pit collapsed, which released methane gas and trapped workers inside.

Around 49 mineworkers were at the mine at the time of the accident.

"Soko coal mine is a dangerous coal mine, dangerous from the aspect of methane," mine manager Drago Milinkovic told RTS.

The mine had implemented safety measures "at the highest level", but the equipment and monitoring apparatus on site were not able to contend with the "sudden release of methane."

"Inspectors, police and all relevant authorities are at the scene, doing what is necessary to determine the cause of this tragedy," AP reported Mining and Energy Minister Zorana Mihailovic as saying.

The mine is located roughly 200 kilometres from Serbian capital Belgrade.

The local hospital in Aleksinac has canceled all non-essential surgery to deal with the mine disaster.

The Soko mine has a history of accidents, Reuters reported. In 1998, 27 coal miners perished in an explosion at the mine. In the previous year, 90 miners died in a fire at a mine close to the area.

Two-thirds of Serbia's power is generated by coal.