Azerbaijani President Ilham Aliyev accused Russia on Sunday of firing at an Azerbaijan Airlines passenger jet before it crashed and of initially trying to cover up the cause of the fatal disaster, demanding that Moscow admit guilt.

Russian President Vladimir Putin apologized to his Azerbaijani counterpart for what he called a "tragic incident" following the crash of an airliner.

A survivor of Wednesday’s Azerbaijan Airlines crash said the plane’s pilots tried to land in Grozny, Chechnya three times, followed by an explosion outside the plane, according to an audio recording shared by Russian TV channel RT.

Russian President Vladimir Putin admitted on Saturday that Russia’s air defense systems were active when Azerbaijan Airlines flight J2-8243 attempted to land in Grozny, Chechnya on Wednesday.

A White House official said the US has seen "early indications" that the fatal crash of an Azerbaijan Airlines plane was caused by a Russian air defense system. White House national security spokesperson John Kirby said on Friday that the US has "seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defense systems.

The Azerbaijan Airlines plane flew hundreds of miles off its scheduled route from Baku to Grozny, and crashed on the eastern shore of the Caspian Sea. Russia's aviation watchdog said a bird strike might have been the cause.

Azerbaijan Airlines says the jet that crashed in Kazakhstan on Christmas Day experienced “physical and technical external interference,” according to an early investigation, as questions swirled about Russia’s possible involvement in the disaster.

There is U.S. intelligence that Russia may have mistakenly shot down an Azerbaijan Airlines flight that crashed in Kazakhstan on Wednesday after misidentifying it as an incoming drone, MSNBC reported on Friday,

There are early indications that a Russian anti-aircraft system may have struck the Azerbaijan Airlines plane that crashed in Kazakhstan, a U.S. official told ABC News.