On Tuesday, China's Ministry of Public Security warned investors to be suspicious of phone calls, e-mails and websites touting supposedly highly profitable stocks.

BBC: NEWS | Business | China shares fall after tax rise

Li Zhuqun, a senior international co-operation official at China's Ministry of Public Security said the gang had now been broken up, but that "efforts to ensure the safety of the Mekong River will continue".

BBC: China parades foreign Mekong killers before execution

China's public security ministry reportedly received word from China's embassy in Venezuela in 2011 of dozens of cases of robbery, kidnapping and extortion targeting Chinese citizens.

BBC: Kidnap ring suspect sent back to China from Venezuela