BEIJING - China's insurance regulator on Wednesday joined the country's concerted effort to stem the massive sell-off in the stock market, easing rules for insurance companies to put money in the market.

Qualified insurance companies will be allowed to invest up to 10 percent of their assets in a single blue chip, increasing from the previous 5 percent stipulation, according to a notice issued by the China Insurance Regulatory Commission.

The limit on the ratio of their equity assets will be further raised to 40 percent from the previous 30 percent, according to the notice.

The move is to optimize the investment portfolio and promote the stable and healthy development in the capital market, the notice said.

The decision followed a raft of other supportive measures aimed at stemming the stock bloodshed that seen the key Shanghai stock index plunging by over 30 percent from the June peak, but the effort seemed to be of no avail.

The benchmark Shanghai Composite Index sank 6.97 percent to open at 3,467.4, while the Shenzhen Component Index opened 4.44 percent lower at 10,870.14 on Wednesday.

Immediately after the market opening, the central bank issued a statement reiterating its liquidity support to stabilize the market and avoid systematic and regional financial risks.