SHANGHAI (AFP) — A man who became an unlikely cult hero in China for murdering six policemen in a revenge attack has defiantly insisted he was not insane when he went on his killing spree, state media reported Tuesday.

An appeal hearing against last month's death sentence for Yang Jia, 28, was held at a Shanghai court on Monday in which his lawyer requested a new psychiatric test to show his client was mentally unstable.

But the unemployed Yang, who was convicted of going on a stabbing frenzy in a Shanghai police station on July 1 in revenge for being wrongfully detained on suspicion of stealing a bicycle, insisted he had no mental disorder.

"I think those cops are mentally unstable," the China Daily quoted Yang telling the court. He added he could remember little from the day of the attack.

After an expert testified Yang was capable of bearing criminal responsibility, judge Xu Wei rejected the request for the new psychiatric evaluation, according to the China Daily.

Yang told the court that when he was held in October 2007 on suspicion of stealing a bicycle, eight policemen beat him for nearly three minutes, the Shanghai Daily newspaper reported.

Police previously confirmed they held Yang overnight, but released him once they were satisfied the bicycle he had been riding was not stolen after all.

Yang's case became a lightning rod for controversy by raising questions about police harassment, with some regarding him as a victim who stood up to abuse commonly suffered by marginalised people in Chinese society.

In a rare protest outside the Shanghai's Higher People's Court as the appeal began on Monday, about a dozen protesters donned T-shirts with Yang's face.

The T-shirts bore a quote from him reading: "If you don't give me a reason then I will teach you a lesson." The protesters were quickly taken away by police.

The one-day appeal hearing, which was requested by Yang's father, concluded without a decision. The court must now deliver a verdict within two weeks, the Hong Kong newspaper Wen Wei Po said.

If the court upholds the guilty verdict, China's Supreme People's Court must ratify the death sentence before he can be executed.

The detailed coverage of Yang's appeal contrasted sharply with the secrecy of last month's initial hearing, prompting critics to question whether Shanghai authorities had given Yang a fair trial.

However, foreign press remained barred from Monday's hearing.