Chinese state television, CCTV, broadcast images of the astronauts outside the new orbital station, installing cameras and other equipment using a 15-metre-long robotic arm.

The footage, captured on Sunday, 4 July, shows astronauts Liu Boming and Tang Hongbo exiting the decompression chamber as the Earth passes beneath them.

According to the Chinese space agency, Liu and Tang spent nearly seven hours outside the station.

The third crew member, Commander Nie Haisheng, remained inside the new orbital station during the maneuvers.

The astronauts arrived on 17 June for a three-month mission aboard China's third orbital station.

The station is part of an ambitious space programme, which recently included the landing of a robot car on Mars in May.

The mission comes as the Communist Party celebrates the 100th anniversary of its founding.

The station's first module, Tianhe ('Heavenly Harmony'), was launched on 29 April, and was followed by a cargo spacecraft carrying food and fuel.

Liu, Nie and Tang arrived on 17 June, aboard a Shenzhou capsule.

China's space agency plans a total of 11 launches by the end of next year to add two more modules to the 70-tonne station.