Russian President Vladimir Putin on Saturday apologised to Azerbaijan’s president for a “tragic incident” which happened in Russian airspace involving an Azerbaijan Airlines passenger plane that crashed after air defences were used against Ukrainian drones.

Flight J2-8243 crashed on Wednesday in a ball of fire near the city of Aktau in Kazakhstan after diverting from southern Russia where Ukrainian drones were reported to be attacking several cities. At least 38 people were killed.

Four sources with knowledge of the preliminary findings of Azerbaijan’s investigation into the disaster told Reuters on Thursday that Russian air defences had mistakenly shot it down.

“(President) Vladimir Putin apologised for the tragic incident that occurred in Russian airspace and once again expressed his deep and sincere condolences to the families of the victims and wished a speedy recovery to the injured,” the Kremlin said in a statement.

“At that time, Grozny, Mozdok and Vladikavkaz were being attacked by Ukrainian unmanned aerial vehicles, and Russian air defence systems repelled these attacks,” the Kremlin said.

The Kremlin said the call took place at Putin’s request.

Ilham Aliyev, Azerbaijan’s president, had noted that the plane had been “subjected to external physical and technical interference in Russian airspace, resulting in a complete loss of control and redirection to the Kazakh city of Aktau,” according to Azerbaijan’s presidential office.

The Embraer EMBR3.SA passenger jet had flown from Azerbaijan’s capital Baku to Grozny, in Russia’s southern Chechnya region, before veering off hundreds of miles across the Caspian Sea.