"The Shenzhou-20 manned spacecraft is suspected of being hit by a tiny piece of space debris, and an impact analysis and risk assessment are under way," the China Manned Space Agency (CMSA) said in a statement.

The return of the spacecraft and the three astronauts, planned for Wednesday, has been postponed to ensure their safety, the statement said.

Chen Dong, Chen Zhongrui and Wang Jie had been expected to touch down at the Dongfeng landing site in northern Inner Mongolia. The CMSA did not give a new date for their return.

A relief crew arrived at the Tiangong space station aboard the Shenzhou-21 last week.

The Tiangong is crewed by teams of three astronauts that are exchanged every six months. It is the crown jewel of China's space programme, into which billions of dollars have been poured in a bid to catch up with the United States and Russia.

Members of both crews were pictured eating "barbecued" chicken wings aboard the station in a video shared by Chinese state media this week.

China has bold plans to send a crewed mission to the Moon by the end of the decade and eventually to build a base on the lunar surface.

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