Nearly 1,000 people took to the streets of the Chinese city of Kunming on Thursday in a renewed protest against a proposed chemical plant, media reports said, with Internet users voicing support.

The gathering outside the Yunnan provincial government office followed a similar demonstration earlier this month, and is the latest example of growing environmental concerns in China, which its new leaders have promised to address.

The Kunming factory will produce paraxylene (PX), a toxic petrochemical used to make fabrics.

Protesters -- some of them wearing face-masks, sun-glasses and caps -- held banners reading slogans including "Kunming mothers seeking health for their babies" and "PX get out", photos posted on major news portal qq.com showed.

A "large number" of police were on the scene to "maintain order" and the area was cordoned off, captions said. Demonstrators engaged in shoving matches with police but there were no serious clashes, according to the website.

Online Chinese text reports appeared to have been censored, with searches for "Kunming" and "PX" leading to messages reading: "The webpage you wanted to browse cannot be displayed for the time being."

But Internet users overwhelmed China's Twitter-like weibo services with support for the protesters.

"There is a riot in the mind of the people of Kunming who are strangled," wrote user "Director Wang Tingting".

Another blogger, "Xi Xiaobudou", said: "Government and media, please do not lie -- we do not want the refinery to come to Kunming."

Others called for an online petition to block the plant.

"I'm the 213,670th citizen to disagree with building the refinery in Kunming... everybody please forward the post and add a number," said "Optimistic V".

According to the official news agency Xinhua, Kunming's mayor Li Wenrong has promised: "The government will call off the project if most of our citizens say no to it."

China sees around 180,000 demonstrations a year on a wide range of issues, including some against proposed chemical plants in what analysts have identified as a rising trend of environmentally-motivated "not in my backyard" protests.

Local authorities in the coastal city of Xiamen cancelled plans for a PX plant after thousands took part in a protest in 2007. A huge protest in the northeastern city of Dalian in 2011 prompted authorities to announce a similar climbdown.