Russia’s aviation chief says that a Ukrainian drone attack was under way in the region of Chechnya at the time an Azerbaijani airliner attempted to land before diverting to Kazakhstan and crashing there.

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.

Azerbaijan is observing a nationwide day of mourning for the victims of the air crash that killed 38 people and left all 29 survivors injured as speculation mounted about a possible cause of the crash

Kazakh authorities have recovered the flight data recorder and an investigation is under way. Shortly after the crash, reports from Russian state-controlled TV said the most likely cause was a strike from a flock of birds.

Russia and Kazakhstan have tried to calm speculation about the cause of the Azerbaijan Airlines plane crash, following claims that it was shot down by Russian air defence systems. On Thursday, Moscow urged calm as its foreign minister said it would be wrong to draw conclusions before an investigation into the crash was complete.