First spacewalk at China's new Tiangong station
On Sunday morning, two of them exited the core module, said the China Manned Space Agency.
The first, Liu Boming, was transported with help from a mechanical arm to a work site and the other, Tang Hongbo, moved by climbing outside the hatch.
In a video clip of Liu leaving the cabin, he exclaimed: "Wow, it's too beautiful out here."
Their mission involves elevating a panoramic camera outside the Tianhe core module, as well as testing the robotic arm which will be used to transfer future modules around the station, state media said.
Television footage showed the astronauts preparing for the spacewalk by donning gear and conducting health checks while exercising.
The crew members were later shown opening the hatch and exiting the module separately, wearing newly developed suits said to weigh some 130 kilograms.
This is the first of two spacewalks planned for the mission, both expected to last six or seven hours.
It is also the first time since 2008 that Chinese astronauts have come out of their craft in space. Back then, commander Zhai Zhigang made China the third country to complete a spacewalk -- after the Soviet Union and the United States.
As with the 2008 mission, the launch of China's first crewed mission in nearly five years is a matter of huge prestige for the country, as Beijing marks the 100th anniversary of the ruling Communist Party this month with a massive propaganda campaign.
To prepare, the crew underwent more than 6,000 hours of training.
The Chinese space agency is planning a total of 11 launches through to the end of next year, including three more crewed missions that will deliver two lab modules to expand the station, along with supplies and crew members.
In addition to Liu and Tang, the mission's commander is Nie Haisheng, a decorated air force pilot who has already participated in two space missions.
He supported the latest spacewalk from within the cabin.
- 'Beyond words' -
On Sunday, state television showed footage of the astronauts' daily lives on Tiangong, including setting up an exercise bike and working out on a treadmill.
One crew member was shown eating with chopsticks, while another did a handstand and somersault after mealtime.
One user wrote: "How much I'm moved by each step of achievement is beyond words."
China's ambition to build an orbiting outpost of its own was fuelled in part by a US ban on its astronauts on the International Space Station, a collaboration between the United States, Russia, Canada, Europe and Japan.
The ISS is due for retirement after 2024, although NASA has said it could potentially remain functional beyond 2028.