China's Shenzhou-21 astronaut crew will stay in space for an extra month, after careful consideration from China's Manned Space Engineering Office, the country's state broadcaster reports.

The Shenzhou-21 space rocket and its crew blasted off atop a Long March-2F rocket from Jiuquan Satellite Launch Centre in northwest China on October 31.

The missions involve trios of astronauts on six-month stays in space. On the current mission are Zhang Hongzhang, Wu Fei - China's youngest astronaut to be sent to space - and Commander Zhang Lu, who flew on the 2022 Shenzhou-15 mission. The three astronauts were ages 39, 32 and 48, respectively, at the time of launch.

They are working closely with the support of the space station's robotic arm and researchers and have successfully completed tasks including installing space debris protection devices and inspecting extravehicular equipment and facilities, CCTV said on Friday, citing the space office.

The trio have been in orbit for more than five months and are in good living and working condition, CCTV said.

The Shenzhou-21 crew were expected to return to Earth around April once they completed their six-month shift. That will now be extended by a month, although CCTV did not give an exact date for their return.

"To further verify the technologies related to long-term astronaut stays in orbit ... it is planned to extend the crew's stay in orbit by approximately one month," CCTV said.

During their spaceflight, the astronaut crew will continue to conduct relevant scientific and technological experiments, it said.