Three Chinese astronauts have returned to earth after spending nearly seven months in space, setting a record for the longest on-orbit stay by a Chinese crew.

The craft carrying Zhang Lu, Wu Fei and Zhang Hongzhang of the Shenzhou-21 crew touched down at the Dongfeng landing site in north China's Inner Mongolia region on Friday evening.

Their return came as China prepares for its first lunar landing by 2030.

The crew had completed various tasks, from processing and transmitting experimental data to transferring remaining supplies, the official Xinhua News Agency quoted the China Manned Space Agency as saying.

They also shared their experience with the Shenzhou-23 crew who arrived at the space station on Monday, Xinhua said.

Xinhua reported earlier that the crew had completed three spacewalk activities.

Zhang Jingbo, the space agency's spokesman, said that Zhang Lu, who was also on an earlier Shenzhou-15 mission to the space station, had completed seven such operations in total - becoming the Chinese astronaut with the most spacewalks, the report said.

Zhang Lu said he felt extremely emotional when he returned to China.

He said at the astronauts' mission would not have been possible without the care and support from their families and comrades, as well as the the backing of leaders and those involved in the project.

Zhang Hongzhang recalled his time away from the planet.

"Looking at earth from space, I really felt that humanity is an indivisible community with a shared future," he said.

One of the three astronauts who arrived at the Tiangong space station with the Shenzhou-23 craft is set to stay for a year.

Tiangong means "Heavenly Palace" in Chinese.

The astronauts are Zhu Yangzhu, the commander, Zhang Zhiyuan and Lai Ka-ying, also identified by Chinese authorities as Li Jiaying, using the Mandarin transliteration of her name.

Lai, who was born and raised in Hong Kong, is the first astronaut from the city on a space mission.

As China steps up its space program, its astronauts have carried out multiple missions to the Tiangong space station, developed after China was effectively excluded from the International Space Station on US concerns over national security.

The United States is seen as China's top space rival, with NASA aiming to land astronauts on the lunar surface in 2028.