The Long March 3B/YZ-1 carrying Beidou satellites 28 and 29 to medium Earth orbit lifts off on February 12, 2018.
The launch was the 267th mission for the Long March rocket family.
China's Beidou satellite constellation grew with the launch of two new navigations satellites, carried into orbit by a single rocket launched from Xichang.
The Long March 3B rocket is used to carry satellites to medium and geosynchronous Earth orbits, and is nearly 55 metres long, with a diameter of 3.35 metres on the core stage.
"China developed a new generation of platform for navigation satellites that enable a single rocket to send two or more satellites into space in 2010", said Wang Ping, the chief designer of BeiDou-3 family.
The launch took place from the Xichang Satellite Launch Center in Sichuan province, using a Long March 3B launch vehicle.
Ground monitoring of a Yuanzheng-1 upper stage deploying a pair of Beidou-3 satellites, launched on November 5, 2017.
The pair launched today are the 28th and 29th satellites for China's Beidou navigation system, China's answer to the US Global Positioning System (GPS), Russia's GLONASS and Europe's Galileo GNSS constellations.
Chinese state media confirmed the launch was a success, and US military tracking data showed the Beidou satellites were orbiting on their planned trajectory inclined 55 degrees to the equator. The Beidou system began providing positioning, navigation, timing and message services to civilian users in China and parts of the Asia-Pacific region in December 2012.
The accuracy, stability and signal strength of the Beidou-3 satellites is improved over previous versions by developments in atomic clocks, laser communications and inter-satellite links.
Beidou is the fourth space-based navigation system in the world, following the GPS in the United States, the GLONASS in Russian Federation and the Galileo of the European Union.
Among eight of its 14 planned missions in 2018, the Long March-3A rocket will send twin BeiDou-3 satellites into space, said Cen Zheng, rocket system commander-in-chief of the mission.
According to plans from the satellite office, the network will be made up of 35 satellites before the end of 2020－several now in orbit will be decommissioned by then－to give Beidou global coverage.
Monday's flight was the seventh of up to 40 space launches planned by China this year. Chang'e 4 will attempt to make the first landing on the far side of the moon.