The three astronauts aboard China's Shenzhou-15 spaceship entered the country's space station and met with another astronaut trio on Wednesday, a historic gathering that added the manpower at the in-orbit space lab to six for the first time.

Chen Dong, the commander of the Shenzhou-14 crew, opened the hatch at 7:33 a.m. (Beijing Time). The three space station occupants greeted the new arrivals with warm hugs and then they took a group picture with their thumbs up, shouting in chorus -- "China's space station is always worth looking forward to."

The space reunion kicked off the first in-orbit crew rotation in China's space station, according to the China Manned Space Agency (CMSA).

The six astronauts are projected to live and work together for about five days to complete planned tasks and handover work, said the CMSA.