Officials in China say a labour rights activist, Zhang Shanguang, is to be tried on Sunday in central Huan province.

Mr Zhang -- who's trial will be closed to the public -- is accused of threatening national security.

The New York-based group, Human Rights in China, says Zhang Shanguang is being tried because he gave information to foreign organisations about farmers' protests and human rights abuses.

Mr Zhang will be the fourth dissident to face trial in two weeks.

He spent seven years in jail for workers' rights campaigning after the pro-democracy demonstrations in 1989.