HONG KONG—China’s central bank said it would reduce the amount of money banks are required to set aside as it moved to stimulate a slowing economy that has been weighed down by a slump in the property market.

It was the second such move this year, after an earlier one in July, in an effort to inject liquidity into the financial system. The measure signals Beijing’s growing concerns about the growth outlook of the world’s second-largest economy, which has been battered in recent months by multiple headwinds. Those include a sharp slowdown in its real-estate market amid a worsening debt crisis at some of its largest property developers and a nationwide power shortage. The potential threat of the Omicron variant of the coronavirus is adding to concerns.