"The spacecraft has shed the third stage. The crew is in high spirits," the commentator of the launch at the Baikonur cosmodrome in Kazakhstan said.
The lift-off of the carrier rocket took place at 7:32 a.m. Moscow time (4:32 GMT). The flight to the orbital space station will take two days, instead of six hours. According to the Russian space agency Roscosmos, the schedule change was made out of security concerns.
The docking with the station is slated for September 4.
The Soyuz crew comprises Russian cosmonaut Sergei Volkov, European Space Agency flight engineer Andreas Mogensen, who will become the first Danish astronaut, and Kazakh cosmonaut Aydin Aimbetov.