The probe into the Azerbaijan Airlines crash in Kazakhstan is examining the conduct of air traffic controllers after the aircraft encountered difficulty, a source said.

The National Resistance Center (NRC) has obtained a letter from Turpal Ilyasov, the representative of Chechen leader Ramzan Kadyrov in Russia's Ural Federal District, containing instructions on how to comment on the crash of an Azerbaijan Airlines plane in Kazakhstan.

Russia has started cooperating with Azerbaijan in investigating the crash of an Embraer 190 aircraft. Officials from four countries will conduct a comprehensive investigation into the cause of the crash,