Thousands of residents in Kunming, capital of Southwest China's Yunnan Province, staged a protest near the provincial government Thursday against a massive oil refinery and paraxylene (PX) project over fears of pollution.

The demonstration against the project initiated by the State-owned China National Petroleum Corporation came after a first wave of protests broke out on May 4. Residents were seen Thursday holding banners and wearing masks that read "No oil refinery and pollution" and "Save our pure land."

Mayor Li Wenrong said at the scene in the afternoon that the public's opinions are valued and will be taken into consideration, and the government will give more details of the project.

A large number of police officers separated the demonstrators, who started to gather around noon, into groups, but no conflicts were seen while residents vented their voice in an orderly manner.

The project, located in the nearby Anning city, is 40 kilometers away from Kunming and would have an annual refining capacity of 10 million tons of crude oil, which is aimed at lessening the severe energy shortage in the region, according to the project description.

The previous protest on May 4 was triggered by the PX project, which is believed by many to be hazardous. Following the demonstration, the city government invited 40 resident representatives on Monday to explain the economic benefit and cutting-edge pollution control technology.

Li reassured the public at the scene Thursday that whether the PX project goes ahead would be at the residents' discretion in July.

Paraxylene is a carcinogenic petrochemical.

Several residents reached by the Global Times in universities, hospitals, government and State-owned enterprises said that they were warned by group text messages not to participate in the protest.

"I'm not that worried after my own research about similar petrochemical projects. What people are complaining about is that they don't trust authorities or the company to really control the pollution," a doctor in the city surnamed Liang told the Global Times.

Ma Xiaojia, director of the provincial energy administration, said Wednesday that the environmental assessment report that the public had been demanding was "confidential."

"Pollution control and environmental impact are no secret.  The contents, except for the confidential parts, should be fully published," Ma Jun, director of the Institute of Public and Environmental Affairs, told the Global Times.

"The biggest environmental issue facing Kunming to take such a huge project is its water shortage," said Wang Xiaochun, professor of environmental sciences with Yunnan University, noting that the city had been suffering from severe drought for four years.