Thousands of people gathered Sunday in southern China to protest against a proposed trash incinerator, protesters said, as the government sought to allay anger by saying the location was not finalised.

In the latest in a series of protests in China over the feared health impact from development projects, thousands of people marched in Boluo county in Guangdong province against plans for an incinerator which would convert trash to electrical power.

Sunday marked the second day of protests. On Saturday more than a thousand people took to the streets, blocking traffic and prompting police to detain 24, according to the local government and police.

"We are on the square right now, at least four to five thousand people gathering here before a march," one protester told AFP by phone on Sunday morning.

Protesters later marched from a public plaza to the offices of the county government.

The demonstration was largely peaceful, though some claimed there were tussles with police. Marchers also took a break for lunch.

Photos posted online showed them carrying professionally printed banners, one reading "Love my Boluo, overturn the garbage dump". A line of riot police, carrying shields and wearing helmets, guarded one intersection.

Huizhou city, which administers the county, sought to defuse the situation, saying hearings would be held to consider public opinion.

"Please everyone use regular channels to reasonably make known opinions and suggestions," it said in a statement on Sunday.

Late on Saturday local police warned people against taking part in "illegal gatherings" and urged them to abide by the law. Authorities detained 24 people for investigation on Saturday but later released eight, police said.

The Boluo county government described Saturday's protest as "generally stable" and promised to listen to public opinion before going ahead with the project, which it described as part of a proposed ecological park.

Analysts say "not in my backyard" protests in China are supported by rising awareness of environmental and health issues, and a growing middle class willing to express their views publicly.

In May 39 people were injured and 60 detained in a violent protest over a waste incinerator in Hangzhou city, a project which local officials later suspended.

Police also detained 18 people over massive rallies opposing a chemical plant in Maoming, also in Guangdong, after thousands of demonstrators took to the streets for days of protests in March this year.

Authorities in the coastal city of Xiamen cancelled plans for a plant producing paraxylene, a chemical used to make fabrics, after thousands took part in a protest in 2007.