A Chinese activist who was investigating whether shoddy construction was to blame for the collapse of thousands of school buildings in the massive 2008 Sichuan earthquake has been sentenced to five years in prison for subversion, AFP reports.

Environmental campaigner and writer Tan Zuoren had earlier been found guilty of "inciting subversion of state power" after he published articles criticizing China's handling of the Tiananmen crackdown in 1989 on the internet, said one of his lawyers, Pu Zhiqiang.

Tan was arrested when he was probing the deaths of thousands of children when their schools collapsed in the May 12, 2008 quake. All in all, about 88,000 people died in the tragedy.

Pu told AFP that Tan was jailed on charges related to the Tiananmen incident, and that none had been raised against him as a result of his quake investigation.

According to Amnesty International, there is reason to believe that Tan's independent investigation was likely the real reason for his detention.

Tan, who had pleaded not guilty, plans to appeal, his lawyer said.

Many parents of children that lost their lives, buried under their school buildings, have called for investigations into whether corruption had contributed to the scale of the destruction and high death toll from the natural disaster.

Amnesty International condemned the verdict, calling it unfair and is demanding Tan's release, AFP says.