China's securities regulator published a list of 258 illegal margin lending platforms and their operators on Wednesday to try to tame a bull run on the country's stock markets.

Shares in the Chinese mainland closed at multi-year highs on Wednesday, extending their winning streak to a seventh session, as hopes of an economic recovery, driven by regulatory and retail support, fueled the market's rally.

Illegal lenders pitch their business via phone apps and social media advertisements, promising potential investors a fast fortune, China Securities Regulatory Commission (CSRC) said in a statement on its website.

Securities margin financing can only be conducted by brokerages, CSRC said. Individuals or institutions are not allowed to do margin lending unless they obtain regulatory approvals.

Illegal margin lending was blamed for China's 2015 boom-bust market volatility.