Mobile phone footage circulating online appeared to show the Azerbaijani Airlines plane making a steep descent before slamming into the ground in a fireball in western Kazakhstan.

After an Azerbaijan Airlines jet crashed in Kazakhstan, speculation mounted about why the plane went down and whether possible Russian air defense action may have played a role.

The damaged plane was denied permission to land at any Russian airports, despite requests from the pilots, and was directed to continue across the Caspian Sea towards Aktau, Euronews reported.