Russia’s president is said to have blamed birds or a Ukrainian drone for a Dec. 25 crash of an Azerbaijani plane. Azerbaijan says Russian air defenses were at fault.

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.”

The leader of Azerbaijan criticized the Russian response to the crash of a passenger jet that Azerbaijani officials said had most likely been hit by Russian air defenses.

President Vladimir V. Putin of Russia told the Azerbaijani leader, Ilham Aliyev, in a phone call, “that the tragic incident took place in Russian airspace.”

Flight attendants and a passenger described the moments before an Azerbaijan Airlines flight went down in Kazakhstan, killing dozens.

Russian aviation authorities said the Azerbaijan Airlines plane had hit a flock of birds. But some experts cast doubt on that account, pointing to footage showing apparent holes in the fuselage.