The reporter, Lan Chengzhang, 35, had been working for the Shanxi office of the newspaper China Trade News since January 3.

On January 10, Lan visited an unlicensed coal mine in Hunyuan County in the province with his colleague Chang Hanwen.

Some reports said the two reporters - who were not accredited journalists - were investigating into the mine, while others suggested that they may have been trying to extort money from the mine owner.

When they arrived at the mine, Lan told an employee, Zhang Gengen, that they wanted to talk with the mine boss, Hou Zhenrun, as they had received reports the mine was run illegally.

Zhang gave the two reporters Hou's telephone number. Hou, who was in Dadong City, suggested they meet there but Lan insisted on waiting for Hou at the mine.

When Hou arrived at the mine that afternoon he was accompanied by eight thugs. The thugs immediately set upon Lan and Chang with clubs, and fled the scene after the beating.

The next morning Lan died of a brain haemorrhage in hospital. His colleague Chang suffered a broken right arm plus minor injuries in the attack.

According to the police, Lan told Chang en route to the coal mine that the mine owner could "give us at least USD 128 once we show him our identity," Xinhua news agency reported.

Lan had an employee card issued by the Beijing-based newspaper, according to the head of the paper's Shanxi office. On three months probation, he had not yet obtained his press card issued by the State Press and Publication Administration. The head of the China Trade News Shanxi office said the two men were employed by the paper but were not authorised to conduct reporting missions and their investigation of the coal mine was a "personal initiative".

The owner of the illegal coal mine, Hou Zhenrun, gave himself up to police late Friday night.

China's huge coal mine sector is ridden with corruption, which is also one of the main causes for the high rate of mine accidents in the country's coal industry.

There were 2,945 coal mine accidents in China last year in which 4,746 people died, equivalent to 13 miners dead per day.