Azerbaijan’s leader on Monday accused Moscow of carrying out a “cover up” over a passenger jet crash last month that claimed 38 lives, as relations sour between the two neighbors.

Russian President Vladimir Putin apologized for the “tragic incident,” which left 38 people dead, though he stopped short of taking responsibility.

Azerbaijan's president said on Monday that Russia was "guilty" over the downing of an airline last month that Baku says was shot by Russian air defenses. An Azerbaijan Airlines Embraer 190 jet crash-landed in Kazakhstan on Dec.

Azerbaijan President Ilham Aliyev said Russia is behind the Christmas Day crash of an Azerbaijan Airlines plane in Kazakhstan, which killed 38 of the 67 people aboard. The motives of the incident remain unclear.

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 in the crash while 29 survived.

Azerbaijani President Ilham Aliyev blasted Russia for putting forward “absurd” theories initially and said Moscow must compensate victims’ families.

In the crash’s aftermath, Azerbaijan has unleashed rare and stinging criticism of Russia, with the country’s president saying Moscow’s response has caused “surprise, regret and rightful indignation.”