Police stepped in to break up fighting between the workers, largely from Sichuan province, and the locals in Shaxi township in Guangdong province on Monday night, the Information Centre For Human Rights and Democracy said.

At least 30 people were injured and two police cars smashed during the rioting that erupted as police arrived at the scene, the centre said.

Guangdong, located next to Hong Kong and known as the ''world's factory floor'', has employed tens of millions of migrant workers in recent decades, a pool of cheap labour that has driven China's export-oriented economy.

''The riots started yesterday [Monday] noon, but escalated late last night, several thousands of people were protesting,'' Liu Tianjin, a Shaxi factory worker, said by phone.

''There were lots of riot police outside last night, and there are still many outside now. I can tell you more than 30 people were injured.''

Both Mr Liu and the centre said the unrest started following a street fight between a migrant youth and a young local man.

Police in Shaxi confirmed the unrest.

''We are now working on it. There are many police officers posted outside the Shaxi government,'' a local policeman said.

Unrest among migrant workers in Guangdong has increased in recent years, with many migrants complaining of discrimination and unfair social benefits provided by local governments.

In November last year, more than 7000 workers went on strike at a Guangdong factory making New Balance, Adidas and Nike shoes, clashing with police in a protest over layoffs and wage cuts, a rights group said.

In June 2011, riots also erupted in the suburbs of Guangzhou, the provincial capital, after rumours spread that police had beaten a street hawker to death and manhandled his pregnant wife, both of whom were from Sichuan.

AFP