Thousands of rescuers were searching for bodies in the Black Sea as Russia marked a day of mourning Monday following the crash of a Syria-bound military plane carrying 92 people.

The Tu-154 jet, whose passengers included more than 60 members of the internationally-renowned Red Army Choir who were heading to entertain Russian troops in Syria for the New Year, went down off the resort city of Sochi shortly after take-off Sunday.

The first 10 bodies have been flown in to the capital Moscow amid a national outpouring of grief. 

Investigators have yet to confirm the cause of the crash, but Transport Minister Maksim Sokolov told a televised briefing Monday that authorities do not believe the plane was taken out by a terrorist attack.

"There could be various causes -- they are being analysed by specialists, experts, the Investigative Committee," he said, adding that active theories ranged from human error to a problem with the fuel.

"Currently the main versions do not include an act of terror," he added.

More than three thousand workers laboured through the night, racing to find the remaining bodies and debris -- including the black boxes crucial to tracking the plane's final moments -- before the currents carry them further away from shore. 

The search operation included 39 vessels covering over 100 square kilometres (38 square miles), with planes, helicopters and drones searching from above and deep-water equipment and divers hunting below the surface.

"I think we will be able to find the location of the plane on the bottom of the Black Sea today," Viktor Bondarev, the commander of the Russian air force, told Russian agencies.

"When we find the plane, we will raise the flight recorders to the surface. We know they are located in the tail and I am sure that the tail was damaged the least," he said.

Sokolov said some of the bodies could have already been carried off by the current to Abkhazia, the separatist region of Georgia.

"Eleven bodies and 154 (body) fragments were found over the first day," defence ministry spokesman Igor Konashenkov said in a briefing. 

"The search is complicated by the large depth range and the sea bottom relief characteristics in the presumed crash area," he said.

Along with the first ten bodies, 86 body parts were flown to the capital for DNA analysis, he added.

- Choir 'orphaned' -

The passenger jet went down at 5:25 am (0225 GMT) on Sunday morning minutes after taking off from Sochi's airport, where it had stopped to refuel after flying out from the Chkalovsky military aerodrome in the Moscow region.

Onboard were 64 members of the Alexandrov Ensemble -- the army's official musical group, also known as Red Army Choir -- and their conductor Valery Khalilov.

"The ensemble has been orphaned by a third," said state channel Rossiya.
The choir was set to perform for Russian troops deployed in Syria during New Year's celebrations at the Hmeimim airbase, which has been used to launch air strikes in support of Moscow's ally President Bashar al-Assad.

Other passengers included military officers, journalists and popular charity worker Elizaveta Glinka, also known as Doctor Liza, who had been flying with a cargo of medical supplies for a hospital in the coastal city of Latakia.

President Vladimir Putin ordered a national day of mourning on Monday, with state television flashing black and white pictures of the victims across the screen while entertainment programmes were cancelled.

People brought flowers to improvised memorials at the port in central Sochi and the city's airport, as well as to the Moscow headquarters of the Red Army Choir and the office of Fair Aid, the NGO that Glinka headed, which primarily worked with Moscow's homeless.

Tu-154 aircraft have been involved in a number of accidents in the past and are no longer used by commercial airlines in Russia. 

But Sergei Bainetov, the air force head of flight safety, said Saturday that this particular plane was "in good condition technically". 

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.

Source: AFP