Azerbaijan Airlines flight J2-8243 came down near the city of Aktau in Kazakhstan after diverting from an area of Russia in which Moscow has used air defence systems against Ukrainian drone strikes in recent months.
The Embraer passenger jet had flown hundreds of kilometres off its scheduled route from Azerbaijan's Baku to Grozny, in Russia's southern Chechnya region.
It crashed on the opposite shore of the Caspian Sea after what Russia's aviation watchdog said was an emergency that may have been caused by a bird strike.
Officials did not explain why it had crossed the sea, but the crash happened after Ukrainian drone strikes this month hit Chechnya.
The nearest Russian airport on the plane's flight path was closed on Wednesday morning.
One of the Azerbaijani sources familiar with the Azerbaijani investigation into the crash told Reuters that preliminary results showed the plane was struck by a Russian Pantsir-S air defence system, and its communications were paralysed by electronic warfare systems on the approach into Grozny.
There is speculation the airliner may have been hit by some form of anti-aircraft fire. (AP PHOTO)
The source said: "no one claims that it was done on purpose. However, taking into account the established facts, Baku expects the Russian side to confess to the shooting down of the Azerbaijani aircraft".
Kazakhstan's transport prosecutor for the region where the plane came down said its investigation had not yet come to any conclusions about the crash.
Kazakh Deputy Prime Minister Qanat Bozymbaev said he could neither confirm nor deny the thesis that Russian air defences downed the plane.
The Kremlin, asked before the Reuters report about the idea that the aircraft had been shot at by Russian air defences, said that an investigation was ongoing and that it would be improper to comment until the inquiry came to its own conclusions.
"It is wrong to build hypotheses before the conclusions of the investigation," Kremlin spokesman Dmitry Peskov said.
Videos of the crash site posted on social media and verified by Reuters showed what appeared to be shrapnel damage to the wreckage of the tail section of the plane.
Aviation security firm Osprey Flight Solutions said in an alert to airlines on Wednesday that footage of the wreckage and the circumstances around the airspace in southwest Russia indicated the possibility that the airliner was hit by some form of anti-aircraft fire.
Russia's Dagestan and Chechnya regions have been targeted by Ukrainian weaponised military drones this month, with Russian air defences activated in response, Osprey said.
Earlier on Wednesday, the Russian defence ministry had reported the downing of 59 Ukrainian drones over several regions, it said.
Some were reportedly downed in closed air space over regions bordering Ukraine, including the Sea of Azov.
Flight operations were reportedly temporarily suspended at Russia's Kazan Airport due to the activity.
In addition, publicly available ADS-B flight tracking data shows that the aircraft experienced GPS jamming throughout its flight over southwest Russia, the alert said.
In Brussels, NATO called for a full investigation into the cause of the crash.
"Our thoughts and prayers are with the families and victims of Azerbaijan Airlines flight J28243," NATO spokesperson Farah Dakhlallah said on X.
Our thoughts and prayers are with the families and victims of — NATO Spokesperson Farah Dakhlallah (@NATOpress) #AzerbaijanAirlines flight #J28243. We wish those injured in the crash a speedy recovery and call for a full investigation.December 26, 2024
"We wish those injured in the crash a speedy recovery and call for a full investigation."
Kazakhstan's senate chairman said earlier on Thursday that the cause of the plane crash was still unknown.
