Media playback is unsupported on your device Media caption Images of violence are being deleted from the internet by the Chinese authorities, as the BBC's John Sudworth reports

Authorities have condemned an environmental protest in southern China that turned violent, calling it "serious criminal behaviour".

Residents in Maoming, Guangdong province, on Sunday protested against the construction of a petrochemical plant that manufactures paraxylene.

Violence broke out, with reports of several injured protesters. On Tuesday, the protests spread to Guangzhou.

Protests are rare in China, where it is illegal to protest without a permit.

Hundreds of Maoming residents marched on the streets on Sunday, protesting against the proposed plant. Some protesters said turnout was more than 1,000.

Clashes with police broke out, with reports of tear gas being fired at protesters. Photos and videos posted on Chinese social media appeared to show injured protesters, police chasing demonstrators with batons, and burning cars.

Smaller protests appeared to continue, spreading to Guangzhou, the provincial capital, on Tuesday.

'Chaos'

A Maoming Daily article, carried on the Maoming government website, said: "On [Sunday] afternoon, a small number of protesters disrupted traffic, before gradually dispersing.

Image copyright Reuters Image caption Riot police were deployed as crowds took to the streets protesting against the proposed plant

Image copyright Reuters Image caption Here, a protester holds a sign saying "opposed PX, return my clean land"

Image copyright Reuters Image caption Demonstrations continued into the early hours of Tuesday

"But after 22:30, a small group of trouble-makers on motorcycles threw stones and water bottles, damaging public facilities."

The Maoming government has called the unauthorised protest "a serious offence" and urged residents to "trust the government and not give illegal elements the opportunity to cause chaos".

Officials later said that no timetable had been given for the plant's construction, and that the authorities would not proceed without consulting the public.

The government said no one was killed in the protests, but did not say if any were injured.

Sophie Richardson, China director at Human Rights Watch, said: "Accounts and photographs suggest that police may have used disproportionate force against demonstrators in Maoming. Authorities should move swiftly to investigate these claims, and hold those responsible to account."

Paraxylene (PX) is used in plastic bottles and polyesters. However, many in China have expressed health concerns over PX plants.

Environmental protests are growing in number in China, and once again, fuelled by the power of the internet, one such protest has caught the authorities by surprise, the BBC's John Sudworth in Shanghai reports.

In recent years paraxylene has become a focus of environmental protest in China, forcing the delay or cancellation of plants in other cities much to the dismay of the national government, our correspondent adds.