MOSCOW (AP) — Russian President Vladimir Putin apologized to his Azerbaijani counterpart on Saturday for what he called a “tragic incident” following the crash of an Azerbaijani airliner in Kazakhstan that killed 38 people, but made no concessions that Moscow was responsible.

Putin’s apology came as allegations mounted that the plane was shot down by Russian air defense forces trying to repel a Ukrainian drone attack near Grozny, the regional capital of Russia’s Chechen Republic.

An official Kremlin statement released on Saturday said air defense systems fired near Grozny airport as the plane “repeatedly” attempted to land there on Wednesday. It was not specifically said that any of them hit the plane.

The statement said Putin apologized to Azerbaijani President Ilham Aliyev “for the fact that the tragic incident occurred in Russian airspace.”

The complaint said Russia had opened a criminal investigation into the incident and that Azerbaijani prosecutors had arrived in Grozny to take part. The Kremlin also said that “relevant services” from Russia, Azerbaijan and Kazakhstan are jointly investigating the crash site near the city of Aktau in Kazakhstan.

The plane was flying from the Azerbaijani capital Baku to Grozny when it turned toward Kazakhstan hundreds of kilometers (miles) over the Caspian Sea from its intended destination and crashed while attempting to land. There were 29 survivors.

According to a readout of the call by Aliyev’s press office, Azerbaijani President Putin told Putin that the plane had been subjected to “physical and technical interference from outside,” although he also stopped short of blaming Russian air defenses.

Aliyev noted that the plane had several holes in the fuselage and that the occupants suffered injuries “because foreign particles entered the cabin during the flight.”

He said a team of international experts had begun investigating the incident at Azerbaijan’s initiative, but did not provide details. Earlier this week, the Azerbaijani Prosecutor General’s Office confirmed that investigators from Azerbaijan were working in Grozny.

On Friday, a U.S. official and an Azerbaijani minister issued separate statements blaming an external weapon for the crash. They repeated the statements of aviation experts who blamed Russian air defense systems for the crash in response to a Ukrainian attack.

Passengers and crew members who survived the crash told Azerbaijani media they heard loud noises inside the plane as it circled over Grozny.

Dmitry Yadrov, head of Russia’s civil aviation agency Rosaviatsia, said on Friday that Ukrainian drones targeted the city as the plane prepared to land in Grozny in thick fog, prompting authorities to close the area to air traffic.

Yadrov said that after the captain made two unsuccessful attempts to land, he was offered other airports but decided to fly to Aktau.

Earlier this week, Rosaviatsia cited unspecified initial evidence that a bird strike had led to an emergency on board.

In the days after the crash, Azerbaijan Airlines blamed “physical and technical malfunctions” and announced the suspension of flights to several Russian airports. It didn’t say where the malfunction came from, nor were any other details provided.

If it is proven that the plane crashed after being hit by Russian fire, it would be the second fatal civil aviation accident linked to fighting in Ukraine. Malaysia Airlines Flight 17 was shot down by a Russian surface-to-air missile in 2014, killing all 298 people on board, as it flew over territory in eastern Ukraine controlled by Moscow-backed separatists.

Russia denied responsibility, but a Dutch court convicted two Russians and a pro-Russian Ukrainian in 2022 for their roles in shooting down the plane carrying an air defense system that had been brought to Ukraine from a Russian military base.

After suspending flights from Baku to Grozny and nearby Makhachkala on Wednesday, Azerbaijan Airlines announced on Friday that it would also suspend flights to eight other Russian cities.

Several other airlines have made similar announcements since the crash. Kazakh airline Qazaq Air said on Friday it would suspend flights from Astana to the Russian Ural city of Yekaterinburg for a month.

Turkmenistan Airlines, the Central Asian country’s flagship airline, on Saturday suspended flights to Moscow for at least a month due to security concerns. Earlier this week, Israeli airline El Al suspended flights from Tel Aviv to the Russian capital, citing “developments in Russian airspace.”