Riot police have fired tear gas to disperse hundreds of demonstrators in southern China on the fourth day of protests against the planned expansion of a coal-fired power plant.

China's official Xinhua news agency said around 500 people had gathered on a highway Friday in the town of Haimen in Guangdong province when police fired gas cannisters toward the crowd.

Large scale protests began on Tuesday, sparking confrontations between police and villagers. One villager, who declined to be identified, said the plant has made water in a nearby river unusable for drinking.

“Before the power plant came up we could use water from the river to boil tea. Now it's all black.''

The local government has promised to temporarily suspend the power plant project. But demonstrators say they have not heard directly from authorities. They are also demanding the release of several protesters who were detained this week.

Protests in China over corruption, pollution, wages and land seizures have become more common in recent years, in part, analysts say, because of the spiraling growth of the Internet. China currently ranks first in Internet use, with more than 450 million Internet users.