The case has prompted accusations that authorities are retaliating against the protesters after initially conceding to their demands by cancelling the project.

"We admit that radical acts were committed, but that was because mere protesting would not have forced the government to change," Zhang Peihong , a lawyer representing defendant Zhu Baosheng , said.

Zhu is accused of smashing a clock in the lobby of the municipal government's office building, pouring looted liquor from the roof of a car and forcing a city official to wear a shirt emblazoned with pro-environmental slogans.

Zhang said he argued that the case failed to take into account negligence on the part of officials. "We see no sincerity on behalf of the state," the lawyer said.

Government actions leading up to such protests need to be examined and wrongdoing exposed, said Liu Shanying, a political scientist at the Chinese Academy of Social Sciences. "You must investigate both sides, but in this case we haven't seen any scrutiny directed at the officials involved," Liu said.

Despite that, unlawful acts such as assault and destruction of property must be punished, he added. "You should defend your rights within the law."

Pollution is a major cause of unrest on the mainland, where the growing middle class has become more outspoken against environmentally risky projects.

In Qidong , thousands of people stormed the municipal government compound and turned at least one police car on its side at the protest on July 28.

Citing court documents, the state-run said the defendants forcibly broke through a police cordon to attack government buildings, injuring at least 90 officers, damaging several cars and causing property loss of more than 230,000 yuan (HK$283,749). It also said the city's party chief was stripped half-naked after he refused to wear a T-shirt boycotting the project, while the mayor was forced to wear such a T-shirt.