President Vladimir V. Putin deployed Russian armed forces in Syria in September 2015, ostensibly to fight terrorism but primarily to prop up President Bashar al-Assad, the leader of the lone remaining Russian ally in the region, whose forces have been fighting an insurgency for nearly six years.

Russian forces have been instrumental in helping the Damascus government regain the initiative, with the final rebels expelled from the besieged city of Aleppo on Thursday.

Three journalists from Channel One, Russia’s main television station, were on the plane, as were journalists from the Zvezda and NTV television networks, news reports said.

Yelizaveta P. Glinka, a prominent Russian philanthropist and a member of the presidential council on human rights and civil society, was also on the list of people on board. Mr. Putin recently honored Mrs. Glinka with a state award for her human rights and charity work. Valery V. Khalilov, the ensemble’s artistic director, was also on the plane, according to the list of passengers.

Mr. Putin expressed his condolences to relatives of the victims, and he declared Monday a national day of mourning. (Christmas is not celebrated as an official holiday in Russia on Dec. 25, because the Russian Orthodox Church observes it on Jan. 7.)

“First of all, I would like to express my sincere condolences to the families of our citizens, who died today, as a result of an aviation catastrophe over the Black Sea this morning,” Mr. Putin said in St. Petersburg, according to remarks published on the Kremlin’s website.