The Azerbaijan Airlines plane that crashed killing 38 people was downed by a Russian air defence system, according to four Reuters sources.
The Embraer 190 passenger jet was en route from Azerbaijan's capital of Baku to the Russian city of Grozny in the North Caucasus on Wednesday when it changed course.
It crashed around two miles from Aktau in Kazakhstan while making an attempt to land after flying east across the Caspian Sea, killing 38 people and injuring all of the other 29 survivors.
The aircraft had diverted from an area of Russia in which Moscow has used air defence systems against Ukrainian drone strikes in recent months.
Mobile phone footage circulating online appeared to show the plane making a steep descent before smashing into the ground in a fireball.
Other footage showed part of its fuselage ripped away from the wings and the rest of the aircraft lying upside in the grass.
Euronews, citing Azerbaijani government sources, reported a preliminary investigation found a Russian surface-to-air missile was fired at the plane during drone air activity above Grozny, which exploded next to the aircraft, with the shrapnel hitting passengers and cabin crew.
The damaged plane wasn't allowed to land at any Russian airports, despite requests from the pilots for an emergency landing, and it was ordered to fly towards Aktau, the sources told the network.
Kremlin spokesman Dmitry Peskov said earlier on Thursday it would be wrong to speculate before the end of the investigation into the cause of the crash.
Azerbaijan is observing a national day of mourning, with national flags lowered across the country on Thursday.
Traffic stopped at noon, and signals were sounded from ships and trains as the country observed a nationwide moment of silence.
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