BEIJING -?Chinese prosecutors investigated 877 people in the financial sector for bribery or abuse of power between January 2014 and June 2015, the Supreme People's Procuratorate (SPP) revealed on Wednesday.

Nearly 75 percent of them worked in banks, spokesperson Xiao Wei said during a press briefing. The rest were mainly from insurance companies and securities agencies.

More than half of the 877 were suspected of taking or giving bribes, according to Xiao.

Thirty people were investigated in cases each involving at least 30 million yuan (4.7 million U.S. dollars), and the aggregated value amounted to 2 billion yuan.

The SPP also promised to strengthen management of stock brokerages and crack down on insider trading and manipulation of securities and futures markets.

Anti-corruption authorities announced on Tuesday that Zhang Yujun, assistant chairman of the China Securities Regulatory Commission, had been removed from office for "severe disciplinary violations" amid wild swings in China's stock markets in recent months.

The commission also handed a fine of 553 million yuan to Qingdao Donghai Ever-Trusting Fund, one of five companies and individuals confirmed to have rigged the markets, and said it would confiscate its 184 million yuan of illegal gains.