Azerbaijan on Sunday paid tribute to the pilots and passengers of the Azerbaijan Airlines passenger plane that crashed in Kazakhstan killing 38 people after Russian air defences were used against Ukrainian drones.

The statement is the closest officials have come to confirming mounting suspicions that the plane was downed by a Russian air-defense system.

It comes as the head of Russia's civil aviation agency says the situation in Grozny, the plane's destination, was "very complicated" at the time.