Tang Yong, the former party secretary of Dongyang city in the wealthy eastern province of Zhejiang, and ex-mayor Chen Fengwei had been fired, Xinhua cited an official government circular as saying late on Friday.

And punishment or penalties had been meted out to other officials responsible for the incident, Xinhua added.

Thousands rioted in a village outside Dongyang city in April - injuring up to 50 policemen - after rumours spread that two of about 200 elderly women keeping a two-week vigil at an industrial site and protesting against factory pollution died during police efforts to disperse them.

Protesters outnumbered police, who fled the scene after trying without success to tear down sheds and road-blocks set up by villagers outside an industrial park housing 13 chemical factories, sources said at the time.

"The provincial government has set up a special team to investigate the accusations of pollution and shut down those chemical plants thought responsible," Xinhua said in the report.

The protests highlight the environmental price of China's economic growth, as well as mounting dissatisfaction over a widening rich-poor rift. That becomes especially significant because the Communist Party is obsessed with maintaining social stability. Heavily industrialised Zhejiang has seen at least three major demonstrations over industrial pollution this year, including one in August when protesters set fire to factory buildings and police cars at a battery plant.

In 2004, there was a sharp rise in "mass incidents" such as protests, riots and mass petitions, China's top police official, Zhou Yongkang, said this year.