The Russian Defense Ministry says a military aircraft has crashed over the Black Sea, with all the 92 people on board presumed dead.
The Tu-154 airliner was carrying 84 passengers and eight crew members, according to the ministry. Reports earlier said the plane had gone off radar shortly after takeoff from an airport in Sochi on Sunday.
Local news agencies cited the Defense Ministry as saying later that the Tu-154 plane had crashed shortly after taking off from the southern city of Adler, south of the Black Sea resort city of Sochi, at 5:40 local time (0240 GMT).
Major-General Igor Konashenkov, a ministry spokesman, told reporters that no survivors had been spotted in the search operations, which were still underway in the Black Sea.
The ministry also issued a statement, noting that 10 bodies had been recovered off the coast of Sochi, with authorities pledging to dispatch more than 100 divers to aid in the search.
"Fragments of the Tu-154 plane of the Russian Defense Ministry were found 1.5 kilometers (0.9 miles) from the Black Sea coast of the city of Sochi at a depth of 50 to 70 meters (165 to 230 feet)," the ministry added.
Military servicemen, journalists, and musicians had been on board.
The ministry said the plane was conducting a routine flight to Russia’s Hmeimim airbase outside the coastal Syrian city of Latakia. Russia has been carrying out a bombardment campaign against militants in Syria on a request from Damascus. It has two airbases in Syria.
Russia’s Investigative Committee said technical personnel responsible for preparing the plane for takeoff were being questioned to determine whether safety regulations had been violated.
Some reports said piloting error was also a possibility.
Putin declares national mourning on Monday
President Vladimir Putin has announced that the country will observe a national day of mourning on Monday.
"Tomorrow Russia will declare a national day of mourning," Putin said on state television.
Assad condoles with Putin over plane crash
Syrian President Bashar al-Assad has also sent a message to Putin telling his Russian counterpart that he is "extremely sad" over Russian plane crash. Emphasizing that the mishap will not hinder the two countries’ joint war against terrorism, Assad said the two countries were partners in the "fight to lay the foundations of stability, security and peace" in Syria.
"Our prayers are with you ... our sorrows and joys are one," Assad told Putin in his message, adding, "The plane had dear friends who had come to join us and the people of Aleppo in their joy with victory and Christmas feasts."
Tu-154 aircraft, like the one in the Sunday incident, have been involved in accidents before. In April 2010, high-ranking Polish officials, including then-president Lech Kaczynski, were killed when a Tu-154 airliner crashed while approaching the Smolensk airport in western Russia.