Some in the crowd waved white signs saying 'Oppose the incinerator, protect green Guangzhou' while others wore surgical masks or dressed in T-shirts emblazoned with environmental slogans. One protester wore a gas mask.

Among the crowd were dozens of residents of Likeng village, who alleged that cancer cases and deaths in their area rose sharply after an incinerator was built there in 2005.

Protesters were surrounded by hundreds of police officers, who ordered the crowd to leave. By mid-afternoon, police used crowd control barriers to separate the protesters, who dispersed peacefully.

A protester who lives near the site of the planned incinerator said residents' complaints for months had gone unheeded.

'I hope that they have heard us this time, and that they will take us seriously now,' she said, declining to give her name.

A recent survey by the Guangdong Provincial Social Research and Study Centre cited by China Daily showed 97 per cent of respondents opposed the construction, and 92 per cent of respondents said the project would seriously harm the environment and their health.

City officials said at a press conference on Sunday that construction of the incinerator would not start until environmental assessments were approved, although they insisted that it was still 'the right option for us'.

The new waste incinerator is expected to replace two overflowing landfills in the district, whose population of 2.5 million produces an average 1,650 tonnes of rubbish a day.

The government had said it expected some 2,200 tonnes of rubbish a day by the end of next year, China Daily reported.

Another resident questioned why the authorities still insisted on going ahead with the plan even though most residents were opposed to it.

'You just can't trust the government's words,' said the resident, surnamed Wang, who pointed out that residents were in the dark until two months ago.

According to state media reports, local planning authorities issued a document on the site selection in 2006, and the plan was approved by the land authorities in April.

Officials have insisted that only equipment meeting international standards would be used at the plant and the emission of dioxins and other pollutants would be controlled.

According to a report published by Greenpeace, a typical incinerator releases carcinogenic dioxins, lead, cadmium, mercury and fine particles into the atmosphere.

A study on people living and working near incinerators in Britain reviewed by Greenpeace showed a doubling in cancer deaths in children living nearby. Another study, on residents living in an urban area near an incinerator in Italy, found a 6.7-fold increase in lung cancer.

Edward Chan Yue-fai, campaign manager for Greenpeace China, said even if dioxin emissions were low, it tended to accumulate in soil, the food chain and human bodies.

Environmental awareness among mainlanders has been growing as living standards improved in recent years. Protests over environmental concerns have also increased.

Just last week, more than 200 residents in Guangzhou's Xintang town protested and blocked a main road over the construction of a sludge- incineration plant.