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.”

Russian President Vladimir Putin apologized for the plane crash in Russian air space on Christmas Day that left 38 people dead in a statement that said Russia was targeting Ukrainian drones over the plane’s planned destination at the time, but stopped short of taking responsibility.

Authorities in several countries are working to determine what caused the deadly crash of a passenger plane yesterday in Kazakhstan. Russian aviation officials initially blamed birds, but investigators are now focusing on the possibility that a Russian air defense system struck the plane.

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

Early indications’ suggest Russia shot down an Azerbaijan Airlines flight that crashed in Kazakhstan on Christmas Day, the White House said on Friday.

Several passenger plane crashes have occurred worldwide this year, including a Wednesday morning Azerbaijan Airlines wreck that has left dozens feared dead.

Two U.S. military officials told NBC News that they had intelligence indicating that Russians may have misidentified the plane and shot it down.

Azerbaijani leader Ilham Aliyev is demanding answers, saying Vladimir Putin's latest apology "isn't enough" and that Moscow must take responsibility.

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.