A Russian military jet crashed on Tuesday while taking off Syria’s Hmeimim base, Russian news agencies said.
The crew members of the Sukhoi jet were killed in the incident, said a military spokesman.
"The Su-24 plane rolled off the runway and broke up while accelerating for takeoff... The plane's crew did not have time to eject and died," the spokesman said.
He did not clarify how many people died, but the Su-24 usually has a crew of two.
"According to a report from the scene of the accident, the reason could be a technical failure," he added.
The Russian Defense Ministry confirmed the crash in a brief statement.
Russian news agencies quoted the ministry as saying the cause could have been technical malfunction.
The crew in Tuesday’s crash was bound on a combat mission.
The latest casualties put the toll of Russian servicemen officially reported killed in Syria at 37.
Last month a Russian general was killed near the eastern city of Deir al-Zour, where Russian special forces are participating in the regime's ground offensive.
Russia has staged air strikes in Syria in support of the regime of Bashar al-Assad since 2015.
On Tuesday, the defense ministry said Russian planes are currently carrying out 150 strikes per day in eastern Syria against ISIS.