BEIJING (AP) -- About 200 people demonstrated in southwestern China against the building of a petrochemical plant they say will pollute their city, state media reported Monday.

The Beijing News said the protest march Sunday in Pengzhou, near the provincial capital of Chengdu in Sichuan province, lasted two hours and was peaceful.

The protesters oppose plans to build an 800,000-ton-a-year ethylene plant and oil refinery, it said. The refinery would process 10 million tons of crude a year, the newspaper said.

''Because they are concerned that these two plants will seriously pollute Chengdu's air and water, the people of Chengdu used today's walk as a way to protest,'' the newspaper quoted one unidentified resident as saying.

China's National Development and Reform Commission approved the refinery's construction at the end of April. The contract was signed in March 2007 with the local government.

A spokesman for the Sichuan Environmental Protection bureau defended the project, saying it meets government environmental standards.

''Scientists and experts have already researched the potential impact the project will have on the environment and have determined that the factory will not harm its surrounding environment,'' said the official, who gave only his surname, Peng.

''Public and media concern over the issue is a positive thing, but they are not the experts, and we must respect the opinion of these experts,'' he said.

Ethylene is a common industrial chemical that can be fatal in high concentrations.

A spokesman for the Pengzhou government who refused to give his name said he had not heard of the protest. Officials who answered the telephone at the Chengdu police and government offices also said they had not heard of it.

Environmental protests have grown in China, especially among members of the growing middle class concerned about the effect of pollution on their quality of life.

Last May, Tenglong Aromatic PX (Xiamen) Co. Ltd. was forced to halt construction of a US$1.4 billion (euro910 million) facility to produce the petrochemical paraxylene in the southern port city of Xiamen after residents sent more than 1 million text messages warning of possible pollution problems.