Beijing - China has sentenced an online activist to three years in prison after convicting him of subversion for supporting Tibetans who staged anti-Chinese protests, a rights group said on Saturday.

A court in the south-western city of Chengdu, Sichuan province, sentenced Chen Daojun on Friday after finding him guilty of "inciting subversion of state power", the Chinese Human Rights Defenders (CHRD) said in a statement.

The charges against Chen, 40, were linked to his posting online of articles supporting Tibetans who staged widespread, often violent protests against Chinese rule in March 2008.

Chen, a freelance writer, was unhappy with the court's verdict but was still considering whether to appeal, the group said.

His lawyer had entered a plea of not guilty with the court, arguing that Chen had the right to "free expression of his political views," it said.

The court tried Chen on an apparently more serious charge of "inciting secession" and it was not clear why he was convicted of subversion instead, the group said.

"CHRD believes that Chen has been imprisoned solely for the peaceful activities of expressing his opinions," it said.

It said state prosecutors focussed on three articles written or posted by Chen, including one called "The government forces the people to rebel: A tribute to the Tibetans who staged a heroic struggle."

Chinese police detained thousands of Tibetans earlier this year following independence protests and riots in many Tibetan areas.

Virtual martial law was imposed in some areas after pro-independence demonstrations and unrest began in Lhasa, the capital of the Tibet Autonomous Regional capital, in early March.

The Chinese government said 19 people were killed in rioting from March 14 in Lhasa but the Tibetan government-in-exile said about 140 people were killed, most of them Tibetans shot by Chinese police.

Protests erupted in dozens of other Tibetan areas of China, including several in Sichuan. (dpa)