The three astronauts of the Shenzhou-19 spaceflight mission have entered the Tiangong space station and met with three others, starting a new round of in-orbit crew handover.

The Shenzhou-18 crew opened the hatch at 12.51pm on Wednesday (Beijing time) and greeted the new arrivals, according to the China Manned Space Agency.

The six crew members then took group pictures for the fifth space get-together in China's aerospace history. They will live and work together for about five days to complete planned tasks and handover work.

The Shenzhou-19 astronauts – Cai Xuzhe, Song Lingdong and Wang Haoze – will stay at the Tiangong space station for approximately six months and conduct a series of experiments.

The Shenzhou-19 blasted off early Wednesday morning atop a Long March-2F rocket.

China declared the launch a "complete success".

The Shenzhou-18 crew, meanwhile, is set to return to Earth on Monday. (Reporting by Xinhua)