Authorities in southern China moved Wednesday to defuse an outbreak of unrest, agreeing to free villagers detained for protesting land seizures and suspending a power plant project.

The wealthy province of Guangdong has seen an upsurge in protests in recent months, as middle-class Chinese become increasingly willing to take on the government on issues ranging from official corruption to pollution.

On Wednesday, a senior provincial official held talks with representatives of Wukan, a fishing village that has become a thorn in the government's side, to try to persuade them to end an embarrassing stand-off with authorities.

Deputy provincial party secretary Zhu Mingguo agreed to free three village leaders detained on December 9 and to release the body of a fourth who died in police custody to his relatives, village spokesman Lin Zulian said.

A police blockade that had surrounded the village since the men were arrested has now been removed and a 10-member government team will go to Wukan to investigate the villagers' complaints.

"I'm very satisfied with the outcome of the meeting," Lin told the residents of Wukan after the meeting. "This is not a victory, but it is a beginning."

The decision to send a senior provincial official to deal with the dispute is an indication of how concerned the Guangdong government was by the rare revolt against authorities in Wukan.

It came as thousands of people in the nearby town of Haimen clashed with police after storming a government building to protests against plans to expand a coal-fired power plant they said was damaging their health.

Neither protest has received much coverage in China's state-run media, but the province's proximity to Hong Kong, with its independent media, means that news of both has has got out, apparently worrying authorities.

Officials overseeing Haimen, which is also in Guangdong, said in a statement late Tuesday they would suspend the project and refer the case to "supervisory authorities" to handle.

Witnesses said police fired tear gas and beat protesters and there were reports that a 15-year-old boy and a middle-aged woman were killed, although this could not immediately be confirmed.

Oriental TV, a Hong Kong-based television station, said six residents had died and nearly 200 were injured in the violent confrontation.

Online searches for Haimen were blocked on Wednesday, as authorities tried to keep news of the clashes from spreading, but one resident of the town said they planned to continue their protests.

"We haven't heard that the local government will suspend the project. If we hear of that we will stop the protest," a protester surnamed Zheng told AFP by telephone from Haimen.

State media reported last month that a 7.4-billion-yuan ($1.17-billion) expansion of the power plant had failed environmental tests and toxic metals found in local waterways "exceeded the standard level".

Three decades of rapid economic growth have left most waterways in China severely contaminated and protests over environmental pollution are increasing -- particularly in the south, where most of China's factories are located.

Haimen is only around 115 kilometres (70 miles) northeast of Wukan, and while there is no indication that the protests are related, they are evidence of the rising challenge posed by social unrest.

Protests over land seizures are relatively common in China, but the stand taken by the villagers of Wukan -- who drove out local Communist leaders and have effectively been governing themselves since September -- was unusual.

Villagers' anger boiled over with the death in police custody on December 11 of Xue Jinbo, a community leader who they suspect was beaten to death. The government has said he suffered a heart attack.

Spokesman Lin said after talks with Zhu that the issue of stolen land -- which villagers say had been going on for years and has deprived many farmers of their livelihood -- had yet to be resolved.

Nonetheless, there was a mood of relief in Wukan, where villagers were starting to take down protest banners put up when the protest leaders were detained.

Many had long maintained that they remained loyal to China's ruling Communist party, and blamed their problems on a small group of corrupt local officials.

"There was so much pressure on us, people have been so afraid," a villager surnamed Zhuang told AFP. "When I heard that he (Zhu) was coming, I felt a that a great weight was lifted off my heart."