Russian air defences may have shot down an Azerbaijan Airlines flight after misidentifying it, according to US military sources.

Two unnamed officials who spoke to Sky News' US partner NBC News said America had intelligence indicating Russia may have believed the flight was a drone and engaged its air defences.

It added that this was down, in part, due to the plane's irregular flight pattern and altitude.

The report comes after US national security spokesperson John Kirby said on Friday that Washington had "seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defence systems".

He refused to elaborate, citing an ongoing investigation.

The plane had been flying from Azerbaijan's capital Baku to Grozny, the regional capital of the Russian republic of Chechnya, on Christmas Day.

During its flight, it turned toward Kazakhstan and later crashed around two miles from Aktau while making an attempt to land after flying east across the Caspian Sea.

The crash killed 38 people and left all of the 29 survivors injured.

Azerbaijan observed a national day of mourning after the incident - as footage from inside the aircraft emerged.

Azerbaijan's transport minister Rashad Nabiyev told the country's media that "preliminary conclusions by experts point at external impact" and witness testimony did as well.

He added: "The type of weapon used in the impact will be determined during the probe."

Azerbaijan Airlines has since suspended flights to a number of Russian cities.

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A spokesperson for the Kremlin declined to comment on the crash, saying it would be up to investigators to determine the cause.

Dmitry Peskov said: "The air incident is being investigated, and we don't believe we have the right to make any assessments until the conclusions are made as a result of the investigation."

The crash was said to have taken place during a Ukrainian drone attack.

Ukrainian President Volodymyr Zelenskyy blamed Russia in a post on social media.

'As if someone hit me with an axe'

Passengers and crew who survived the crash told Azerbaijani media that they heard loud noises as the aircraft was circling over Grozny.

Aydan Rahimli, a flight attendant, said that after one noise oxygen masks were automatically released and she went to perform first aid on a colleague, Zulfugar Asadov, and then heard another bang.

Mr Asadov said the noises sounded like something hitting the plane from outside.

Shortly afterwards, he sustained a sudden injury like a "deep wound, the arm was lacerated as if someone hit me in the arm with an axe," he said.

Two other survivors described their experiences on the flight.

Jerova Salihat told Azerbaijani television that "something exploded" near her leg and Vafa Shabanova said there had been "two explosions in the sky, and an hour and a half later the plane crashed to the ground."

If proven the plane crashed after being hit by Russian air defences, it would be the second deadly aviation incident linked to the Kremlin's conflict with Ukraine.

Malaysia Airlines Flight 17 was shot down by a Russian missile according to investigators, killing all 298 people aboard, in 2014.

(c) Sky News 2024: Azerbaijan Airlines crash: Russian air defences may