The migrants, all from southwest China's Chongqing Municipality, were working at a construction site of a hydropower station on the Dongjiang River in Dongyuan County of northern Guangdong's Heyuan City.

The workers, who have not been paid for four months, went on strike last Friday, which led to the descent by more than 200 thugs, according to the newspaper.

"The first batch of about 50 gangsters came with spades in their hands, and the second batch had axes, steel pipes and sabres, and there were more behind them," the newspaper quoted Liu Gangqing, one of the migrant workers, as saying.

"They didn't stop lashing out at us even when the police arrived," said another migrant Li Chuanbing.

A doctor with Heyuan People's Hospital told the newspaper that Lei Mingzhong, a victim of the violence, had suffered "brain death" and had virtually no chance of survival.

Huang Juping, a Heyuan government spokesperson, confirmed Lei was in critical condition.

However, he denied there had been a mass assault, saying it was "a violent conflict" involving more than 30 migrant workers and other company staff.

According to Huang, about 100 migrant workers were incited by their employer, Qiutian Construction Co. based in Shenzhen city, to ask for a rise from Fuyuan Hydropower Development Co., the proprietor of the hydropower station.

Qiutian company said it had held back workers' pay because Fuyuan refused to compensate it for losses suffered when some of the company's equipment and tools were washed away by flash floods in the summer of 2006.

Wang Guangtao, China's Construction Minister, ordered an "immediate investigation of the incident". Local police have detained four people from Fuyuan company alleged to have been involved in the attack on the migrant workers.

Chased by the gangsters, two workers were forced to jump into Dongjiang River during the attack. But they survived.

The local government has set up a mediation team. Fuyuan has agreed to pay the medical costs of the injured workers. Construction of the hydropower station will be suspended until all "divergences" have been solved between the two companies.