Tiangong’s construction marks a significant step in China’s ambitious space programme. It has already seen China land a rover to Mars and send probes up the Moon.

Three astronauts set off last month to become China’s first crew. They will remain there for three months on China’s longest-ever crewed mission.

Two of them left the station on Sunday morning for seven hours of work in Tiangong’s first spacewalk, according to the China Manned Space Agency.

The space agency stated that astronauts Tang Hongbo and Liu Boming safely returned to Tianhe’s core module, marking the success of the country’s first spacewalk.

State media reported that their tasks included raising a panoramic camera from outside Tianhe’s core module and testing the station’s robotic arm, which will be used for future modules to be transferred around the station.

The astronauts placed foot stops on the robotic arms and with their support, performed other assembly work to add the space agency.

Liu exclaimed in a video clip that he was leaving the cabin: “Wow! It’s so beautiful out there!”

Television footage showed astronauts getting ready for spacewalk by putting on gear and exercising.

Later, Liu and Tang were shown separately opening the hatch and exiting from the module. They were wearing new suits that weighed 130 kilograms.

The mission commander Nie Haisheng supported them from within the station, a decorated pilot of the air force who is currently on his third space mission

This was the first of two planned spacewalks for the mission. Both are expected to last between six and seven hours.

This was also the first spacewalk by Chinese astronauts since 2008. Zhai Zhigang, then China’s third spacewalker after the Soviet Union or the United States, made it so.

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This is China’s first crewed expedition in almost five years. It also comes as a matter of great prestige, as China marks the 100th anniversary this month of the ruling Communist Party with a huge propaganda campaign.

The crew received more than 6,000 hours training to prepare.

Through the end of next years, China’s space agency plans to launch 11 missions. This includes three crewed missions. Two lab modules will be delivered to expand the station and supplies as well as astronauts.