Thousands of residents took part in the demonstration.

Calls for the plant to be moved began mounting last week after a tropical storm broke the dyke around the plant, sparking fears of a toxic spill.

The plant produces paraxylene (PX), a chemical used in fabric manufacture which can be highly toxic.

The city's top official, Tang Jun, had tried to calm the crowd on August 14 by promising to move the plant out of the city, but the protesters showed no sign of dispersing.

There were no reports of injuries in the scuffles during which riot police were deployed to shield the municipal government office.

Calls for protesters to gather on August 14 for a "group stroll", as the rally was termed, had reportedly been circulating on social networks.