BEIJING, April 27 (Xinhua) -- China's Tianzhou-1 cargo spacecraft and Tiangong-2 space lab completed their first in-orbit refueling at 7:07 p.m. Thursday, another success of the Tianzhou-1 mission.

Mastering the technique of refueling in space will help the country to build a permanent space station.

China is the third country, besides Russia and the United States, to master refueling in space.

The in-orbit refueling, under control of technicians on Earth, takes about five days.

A second refueling in space will be conducted in June.

Tianzhou-1, China's first cargo spacecraft, was launched on April 20 from Wenchang Space Launch Center in south China's Hainan Province.

It completed automated docking with the orbiting Tiangong-2 space lab on April 22.