China's courts at all levels tried and concluded 527 cases against mafia-style gangs last year, up 13.8 percent from the previous year, according to a report delivered by the top judge at the annual session of the parliament on Thursday.

The courts convicted 3,231 criminals in these cases last year, up 16.6 percent, it says.

Wang Shengjun, president of the Supreme People's Court delivered the report on the work of the supreme court to nearly 3,000 lawmakers at the Third Session of the 11th National People's Congress.