A Chinese activist who sought compensation for families whose children fell ill or died during a tainted milk scandal in 2008 went on trial Tuesday for provoking social disorder, his wife said.

Zhao Lianhai -- whose own child was one of 300,000 who were sickened in 2008 by drinking milk laced with the industrial chemical melamine, which was added to make products appear higher in protein content -- was arrested in December.

Six children died during the scandal, which led to huge recalls worldwide and cast a harsh spotlight on China's food safety regime. The issue re-emerged earlier this year when tainted milk powder reappeared on the market.

"The trial began this morning, but there is no result as of yet. I don't know what the situation is inside," Zhao's wife Liu Xuemei told AFP by phone.

Liu said she had not been allowed to attend the closed trial in a Beijing court.

Zhao campaigned relentlessly on behalf of victims of the scandal, and also ran a website providing information to the families after their babies suffered from melamine-induced kidney stones and urinary tract infections.

A total of 21 people were convicted for their roles in the scandal, and two were executed.

Tian Wenhua, the former head of the now bankrupt Sanlu dairy company -- which was at the centre of the scandal -- was sentenced to life in prison.

Liu said she was unsure when a verdict in Zhao's case would be reached.