Russia's federal space agency says an unmanned rocket and its payload of two communications satellites failed to reach its target orbit.
Roscosmos said on August 7 that a secondary booster module of the Proton-M rocket carrying Russian and Indonesian satellites switched off earlier than expected after takeoff from the Baikonur cosmodrome in Kazakhstan on August 6.
This was the latest in a series of failures that has dogged Moscow's space program.
Last August, Russia lost contact with a communications satellite shortly after a Proton-M launch.
In 2007, a Proton-M carrying a Japanese communications satellite crashed.
Roscosmos spokesman Alexei Kuznetsov said August 7 that the agency might halt Proton-M launches after an investigation.
The 50-meter long booster rocket with a payload of up to 20 metric tons has been in use since 1965.
Based on reporting by AP and ITAR-TASS