Azerbaijan Airlines, the carrier of the passenger jet that crashed in Kazakhstan on Christmas Day, said preliminary investigations have found the disaster occurred “as a result of physical and technical external interference,

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.

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