In April, police armed with clubs and shields used teargas to break up a rally staged by farmers against the construction of a chemical factory in Huashui township, Dongyang city in Zhejiang province.

The protests turned into riots after an elderly protestor was allegedly run over and killed by a police car. Up to 80 police and other officials were injured in the incident, according to witnesses at the time.

Xinhua news agency said Saturday that local communist party secretary Tang Yong and mayor Chen Fengwei had been sacked, and that an unspecificed number of officials responsible for the incident were also punished.

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

An industrial estate was built in Huashui in 2001 and local people were against the construction of another chemical factory on the site.

They claim factories operating there spew toxic waste and emissions into the water supply, which had resulted in ruined crops and deformities among new-born babies.

China has witnessed a slew of violent demonstrations over the past year, often the result of large-scale construction that is part of the country's economic boom.

Although land and environmental disputes are common, moves by authorities to sack officials for their failure to address problems are still relatively rare.

The move in Dongyang is seen as a concession to placate villagers' anger in the light of the central government's repeated calls for harmony and its rising fear of social instability.

Earlier this month, state media said the official who gave the order for security forces to open fire on village protestors in southern China's Shanwei city was arrested.

Official reports put the death toll at three but residents said dozens were killed in that incident.

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