The ministry told agencies there was no sign of any survivors at the crash site and that four bodies had been recovered off the coast of the city, as authorities launched a frantic search operation.

“Fragments of the Tu-154 plane of the Russian defence ministry were found 1.5 kilometres from the Black Sea coast of the city of Sochi at a depth of 50 to 70 metres,” the ministry said.

President Vladimir Putin told state television that Russia would observe a national day of mourning on Monday.

The plane had been on a routine flight to Russia’s Hmeimim airbase in western Syria, which has been used to launch air strikes in Moscow’s military campaign supporting its ally President Bashar al-Assad in the country’s devastating civil war.

Among the plane’s passengers were Russian servicemen as well as 64 members of the Alexandrov Ensemble, the army’s official musical group also known as the Red Army Choir, and its conductor Valery Khalilov. They were heading to Syria to participate in New Year celebrations at the airbase.

The passengers also included nine journalists, with state-run channels Pervy Kanal, NTV and Zvezda saying they each had three staff on board the flight.

There were also eight crew members, the ministry said.

A list of passengers published by the defence ministry also included Elizaveta Glinka, a doctor and charity worker who serves on the Kremlin human rights council.

Mikhail Fedotov, who heads the council, said Glinka was travelling to Syria to bring medication to a university hospital in the coastal city of Latakia near the airbase, agencies reported.

German Chancellor Angela Merkel, Turkish Prime Minister Binali Yildirim and the US Embassy in Moscow have expressed condolences, among others.

Kremlin spokesman Dmitry Peskov said that Putin was being kept updated on the search operation and was in constant contact with defence minister Sergei Shoigu.

Konashenkov said that Deputy Defence Minister Pavel Popov had flown to Adler along with a team tasked with clarifying the circumstances surrounding the crash.

Transportation Minister Maxim Sokolov, who is heading a state commission probing the crash, is also on his way to the region, the government said in a statement.

The ministry has not put forward any possible causes of the crash.

Konashenkov said that the aircraft had been in service since 1983 and had flown some 7,000 hours since. The plane last underwent repairs in December 2014 and was serviced in September, he said.

Russia’s Investigative Committee said a criminal probe had been launched to determine whether violations of air transportation safety had led to the crash.

Investigators are currently questioning the technical personnel responsible for preparing the plane for take-off, the committee said.

Tu-154 aircraft have been involved in a number of accidents in the past.

In April 2010 many high-ranking Polish officials, including then president Lech Kaczynski, were killed when a Tu-154 airliner went down in thick fog while approaching Smolensk airport in western Russia.