Wang and fellow astronaut Zhai Zhigang left the station's main module on Sunday evening, spending more than six hours outside installing equipment and carrying out tests alongside the station's robotic service arm, according to the China Manned Space agency.

The third member of the crew, Ye Guangfu, assisted from inside the station, CMS said on its website.

Wang, 41, and Zhai, 55, had both travelled to China's now-retired experimental space stations, and Zhai conducted China's first spacewalk 13 years ago.

The three are the second crew on the permanent station, and the mission that began with their arrival on October 16 is scheduled to be the longest stretch of time in space yet for Chinese astronauts.

The Tianhe module of the station will be connected next year to two more sections named Mengtian and Wentian. The completed station will weigh about 66 tonnes, much smaller than the International Space Station, which launched its first module in 1998 and weighs around 450 tonnes.

Three spacewalks are planned to install equipment in preparation for the station's expansion, while the crew will also assess living conditions in the Tianhe module and conduct experiments in space medicine and other fields.

China's military-run space program plans to send multiple crews to the station over the next two years to make it fully functional.

Australian Associated Press