The Shenzhou XX mission crew is on their return journey to Earth and is expected to land in the Inner Mongolia autonomous region later today.

According to the China Manned Space Agency, the Shenzhou XXI spaceship's re-entry capsule carrying the astronauts separated from the Tiangong space station at 11:14 am and entered Earth orbit.

It will re-enter the atmosphere under the command of ground controllers, it said.

The agency explained that the crew's own spacecraft, the Shenzhou XX, was found to have tiny cracks on the viewport window of its re-entry capsule, most likely caused by impacts from space debris.

As a result, the vessel did not meet the requirements for the astronauts' safe return and will remain in orbit to continue relevant experiments, according to the CMSA.

The three Shenzhou XX astronauts - mission commander Senior Colonel Chen Dong and crew members Colonel Chen Zhongrui and Colonel Wang Jie - were initially scheduled to return on Nov 5 after a six-month stay at the space station.