The announcement by the Shanghai and Shenzhen stock exchanges came a day after China's state-owned margin financing loan provider moved to cut brokerages' borrowing costs to promote stock investment.

In margin financing, investors borrow to buy stocks.

The measures are the latest efforts by Chinese authorities to stabilize markets during the week-long Communist Party Congress, which concludes on Sunday.

Qi Wang, founder and CEO of MegaTrust Investment (HK), said the measures "are not a big, big deal, but signs that China is trying to prop up the market,"

China's stock market is struggling to find its feet amid a gloomy outlook for an economy ravaged by spiking COVID cases and a prolonged property debt crisis. The benchmark CSI300 Index has plunged 24% so far this year, among the world's worst performers.

The Shanghai Stock Exchange said that, on its main board, the number of stocks eligible for margin financing and securities lending would be expanded to 1,000 from 800, starting next week.

The move will "help draw additional capital, make the market more vibrant, and improve market liquidity and pricing efficiency," the exchange said in a statement.

The Shenzhen bourse said in a separate statement the number of qualified stocks would be increased to 1,200, from 800, on markets beyond its ChiNext board, where stocks become automatically eligible on debut.

Late on Thursday, the China Securities Finance Co (CSF), which provides loans to securities firms to fund their margin lending businesses, said borrowing rates would be cut across the board by 40 basis points. The cut would allow investors to borrow money more cheaply to buy stocks.

The move is aimed at "promoting more capital to participate in market investments and safeguard stable and healthy development of China's capital markets," the CSF said.

Separately, the CSF also kicked off a market-oriented reform of the margin refinancing business, allowing brokerages to borrow money at more flexible maturities, and at market-competitive rates.

China has taken a series of steps to stabilise its stock and currency markets the during the politically key Party Congress.