Azerbaijan Airlines said “physical and technical external interference” was the cause of a crash this week that killed 38 people flying to southern Russia, the closest officials have come to confirming mounting suspicions that the plane was downed by a Russian air-defense system.

The head of Russia’s aviation authority, however, countered the statement, saying the plane tried to land in Grozny in Russia’s Chechnya region amid difficult conditions during a Ukrainian drone strike. Russia hasn’t responded to leaked preliminary findings of an Azeri investigation that point to the plane being hit by a Russian antiaircraft missile or shrapnel from it.

The aftermath of the crash has struck a blow to relations between the former Soviet republics and led to an uproar in Azerbaijan, a small but increasingly powerful oil-producing country. The state-owned Azeri airline said it was suspending flights from Baku to eight Russian airports in the wake of the crash.

“The aircraft was shot down inside Russian territory in the skies above Grozny. And it is impossible to deny this,” said Azeri parliamentarian Rasim Musabeyov , speaking to Azerbaijan’s Turan Agency. He added that Russia should apologize and take adequate steps to compensate the victims’ families or face a grave deterioration in ties.

“Those who did this should be held criminally liable,” said Musabeyov.

Kremlin spokesman Dmitry Peskov referred to Russia’s own probe. “The investigation is ongoing into this aviation incident and until the conclusions, which will be made in accordance with its results, we don’t have the right to comment,” he told Russian state media.

The plane ultimately crashed in Kazakhstan after being diverted from Russian airspace.

Russia has seen its influence wane in Azerbaijan and the broader southern Caucasus region as Baku has strengthened its ties with Turkey and Israel in recent years. Further deterioration could reduce Moscow’s foothold even more in a region it once considered its strategic backyard.

Suspicions of Russian responsibility arose shortly after the crash when aviation-security firm Osprey Flight Solutions said that the flight “was likely shot down by a Russian military air-defense system,” citing assessments of footage of the crash, the damage to the aircraft and recent military activity.

The plane’s undulating flight path—and a sudden downward turn at a dangerously steep angle before landing—suggests the pilots were struggling to guide it, experts said.

The preliminary conclusions of the Azeri investigation into the crash show that a Russian Pantsir antiaircraft system hit the plane, after which Russian authorities diverted it from its airspace and had its GPS jammed, according to people briefed on the matter. Similar accounts have been leaked to Azeri and Western media in an attempt to boost pressure on Russia, said a person close to the Azeri government.

“We have seen some early indications that this jet was brought down by Russian antiair systems,” said John Kirby , a spokesman for the National Security Council. “That said there is an ongoing investigation now…we have offered our assistance to that investigation.”

The incident has increasingly carried echoes of the downing of Malaysia Airlines Flight 17, which was shot down by an air-defense system used by Russia from Ukrainian territory held by Moscow-backed rebels in 2014, killing all 298 people on board. Russia didn’t accept responsibility for that incident, which led to two Russians being tried in absentia in the Netherlands for the crash.

The incident threatens to increase Russia’s isolation, as several airlines, including Israel’s El Al, Fly Dubai and Kazakhstan’s Qazaq Air, suspended flights to cities in western and southern Russia following the incident. Most European carriers stopped flying to Russia following its invasion of full-scale Ukraine in 2022, and the EU has closed its airspace to Russian airplanes.

The crash also highlights the growing risks the Ukraine war has posed to civil aviation in Russia. Moscow has tried to keep its skies open even as Kyiv has boosted its ability to strike deeper into Russian territory with drones and long-range missiles provided by the U.S.