SHANGHAI, China: China has sentenced 16 people to up to a year-and-a-half in prison for involvement in an environmental protest last July when a crowd of thousands ransacked government offices, the official Xinhua news agency reported.

A court in Qidong city, 65 km (40 miles) north of Shanghai, charged the group of demonstrators with "gathering to assault state organs, damaging property and theft" during the July 28 demonstration against a pipeline for waste from a paper factory.

The protest exemplified a growing environmental awareness and willingness of urban people to voice concern about industrial pollution. At the same time, the ruling Communist Party worries that protests can undermine social order.

Throngs of people marched through the streets before pouring into a government compound where they turned over cars, ransacked offices and tossed documents out of windows.

One of those sentenced on Wednesday was Zhu Baosheng, who state media previously reported forced the Qidong mayor to put on a T-shirt printed with an anti-pollution slogan.

The protest came within days of a similar violent protest in the town of Shifang, in the southern province of Sichuan.

All 16 defendants in Qidong were sentenced to 12 to 18 months in prison, but 13 were given a reprieve on the grounds that they had confessed and repented, Xinhua said. One planned to appeal while the others did not, it said.

The sentences come during a particularly smoggy winter that has renewed widespread concern over China's environmental problems. Air quality levels in Beijing have regularly been labelled as unhealthy or hazardous.