Police in China have detained 72 people after thousands rioted in an eastern manufacturing city in what began as a protest over taxes, local authorities said.

Cars were smashed and several police officers and protesters were injured in the riots, which began last Wednesday in China's eastern Zhejiang province and continued well into Thursday.

It was the largest reported outbreak of unrest in China in recent months and reflects growing resentment among millions of ordinary Chinese left behind by the country's economic boom and their frustration at official corruption.

The riots began when a protest by a factory owner over tax demands in the town of Zhili, a centre for the manufacture of children's clothing, turned violent.

An official statement said Sunday that 72 people had been detained, although only 21 of them were suspected of committing criminal offences.

Another 29 people were given warnings and 95 ordered to write "statements of repentance," it said.

Most factories in the town were closed after the riots last week, but state media said production was gradually returning to normal.

Authorities in Zhejiang have said the tax collector whose demands for money from a clothing manufacturer sparked the riots had been sacked.

AFP calls to the local government on Monday went unanswered.