"He was sentenced to three years on blackmail and fraud charges," his lawyer Yan Bingjie told AFP by telephone after the near seven-hour trial in eastern China's Jiangsu province.

"Wu Lihong looked a bit upset, he said he would appeal."

Wu was additionally fined for 3,000 yuan (396 dollars) and was ordered to return his alleged "illegal gains" of 45,000 yuan.

He was accused of swindling 55,000 yuan out of local businesses, according to the Information Center for Human Rights and Democracy.

The 39-year-old has campaigned for years against the pollution of Taihu lake, which lies in the centre of the Yangtze River Delta plain, a region known for its natural beauty but littered with polluting light industry and chemical factories.

Taihu lake, which borders China's eastern Zhejiang and Jiangsu provinces, is also a major source of drinking water for the heavily populated area including neighbouring Shanghai, China's financial hub.

Wu told the court yesterday that while in jail, he had five days of sleep and food deprivation and was beaten on his back and feet, his sister Wu Liying told reporters earlier.

His wife and several family members attended the trial, after a brief confrontation with court officials who tried to stop them from entering the courtroom, according to an AFP reporter.

Security surrounding the court house was tight and reporters trying to cover the case was heavily monitored by plain clothes officials.

Wu was arrested on April 13 when dozens of police stormed his house, ransacked it and took his computer and personal documents, according to his wife Xu Jiehua at the time.

In an interview with AFP last year, Wu said the government's economic interests continued to take precedence over environmental protection.

"The government and industry are connected to each other like a chain, they are inseparable," he said at the time.

"The central government is good but it can't see what's happening here with the local government colluding with the factories."

Although China has vowed to step up protection of its heavily degraded environment, local politics often trumps national policy and effective independent policing, Wu said.

Wu, who has repeatedly been threatened by the authorities, was last formally arrested in 2002, when police held him for 10 days.