What is known about a plane crash in Kazakhstan that Azerbaijan says was caused by Russia?

Azerbaijan's President Ilham Aliyev said on Sunday that the Azerbaijani airliner that crashed in Kazakhstan on Wednesday, killing 38 people, was shot down by Russia, albeit unintentionally.

Aliyev told Azerbaijani state television that the aircraft was hit by fire from the ground over Russia and rendered uncontrollable by electronic warfare. He accused Russia of trying to ''hush up'' the issue for several days.

Russian President Vladimir Putin on Saturday apologized to his Azerbaijani counterpart for what he called a ''tragic incident'', but stopped short of acknowledging that Moscow was responsible.

Putin's apology to President Ilham Aliyev came as allegations mounted that the plane had been shot down by Russian air defense systems attempting to fend off a Ukrainian drone strike near Grozny, the regional capital of the Russian republic of Chechnya, where the plane was heading.

Here are some things to know about the crash that killed 38 out of the 67 people on board:

How did the plane crash?

Azerbaijan Airlines' Embraer 190 was en route from the Azerbaijani capital of Baku to Grozny in the North Caucasus on Wednesday when it was diverted. It crashed while trying to land near the city of Aktau, Kazakhstan, after flying hundreds of kilometers (miles) east across the Caspian Sea.

Rescuers rushed 29 survivors to hospitals.

What have officials said about a possible cause?

Kazakhstani, Azerbaijani and Russian authorities have said they are investigating the crash. Initial theories put forward by various officials included possibilities of a bird strike, bad weather and an oxygen canister exploding aboard the plane.

Embraer told The Associated Press in a statement that the company is ''ready to assist all relevant authorities.''

Dmitry Yadrov, head of Russia's civil aviation authority Rosaviatsia, said Friday that as the plane was preparing to land in Grozny in deep fog, Ukrainian drones were targeting the city, prompting authorities to close the area to air traffic.

Later on Friday, senior officials in the U.S. and Azerbaijan made separate statements suggesting the plane may have been brought down by weapons fire, echoing those made by aviation experts who blamed the crash on Russian air defense systems responding to a Ukrainian attack.

Rashan Nabiyev, Azerbaijan's digital development and transportation minister, told Azerbaijani media that ''preliminary conclusions by experts point at external impact,'' as does witness testimony.

''The type of weapon used in the impact will be determined during the probe,'' Nabiyev said.

White House national security spokesman John Kirby said that the U.S. has "seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defense systems,'' but refused to elaborate, citing an ongoing investigation.

Those statements echoed assessments by outside aviation experts and raised pressure on Russia.

Some aviation experts have said the holes seen in the plane's tail section after the crash indicate that it could have come under fire from Russian air defense systems fending off a Ukrainian drone attack.

Mark Zee of OPSGroup, which monitors the world's airspace and airports for risks, said that the analysis of the fragments of the crashed plane indicates a 90-99% probability that it was hit by a surface-to-air missile.

Osprey Flight Solutions, an aviation security firm based in the United Kingdom, warned its clients that the ''Azerbaijan Airlines flight was likely shot down by a Russian military air-defense system.''

Osprey CEO Andrew Nicholson said that the company had issued more than 200 alerts regarding drone attacks and air defense systems in Russia since Moscow launched its full-scale invasion of Ukraine in February 2022.

FlightRadar24 said in an online post that the aircraft had faced ''strong GPS jamming'' that interfered with flight tracking data allowing it to monitor the plane's flight path. Russia has extensively used sophisticated jamming equipment to fend off drone attacks.

It's unclear why the pilots decided to fly across the Caspian Sea instead of trying to land in Russia after the plane was hit, he said, adding that they probably faced restrictions on landing at a closer venue and may have thought that the damage was not critical.

In Azerbaijan, Caliber online newspaper also claimed that the airliner was fired upon by a Russian Pantsyr-S air defense system and also had its systems affected by jamming equipment as it was approaching Grozny.

How did Russia's and Azerbaijan's leaders respond?

Aliyev said Sunday that the jet was shot down by Russia, albeit unintentionally.

''We can say with complete clarity that the plane was shot down by Russia. (...) We are not saying that it was done intentionally, but it was done,'' he told Azerbaijani state television.

''Unfortunately, for the first three days we heard nothing from Russia except delirious versions,'' he said.

Aliyev said Azerbaijan made three demands to Russia in connection with the crash.

''First, the Russian side must apologize to Azerbaijan. Second, it must admit its guilt. Third, punish the guilty, bring them to criminal responsibility and pay compensation to the Azerbaijani state, the injured passengers and crew members,'' he said.

Aliyev noted that the first demand was ''already fulfilled'' when Russian President Vladimir Putin apologized to him on Saturday. Putin called the crash a ''tragic incident'' though stopped short of acknowledging Moscow's responsibility.

Kremlin spokesman Dmitry Peskov told Russian state media on Sunday that Putin had spoken to Aliyev over the phone again, but did not provide details of the conversation.

According to a readout of the call provided by Aliyev's press office, the Azerbaijani leader told Putin that the plane was subjected to ''external physical and technical interference,'' although he also stopped short of explicitly blaming Russian air defenses.

Aliyev noted that the plane had multiple holes in its fuselage and that the occupants had sustained injuries ''due to foreign particles penetrating the cabin mid-flight.''

Azerbaijan observed a nationwide day of mourning on Thursday. National flags were at half-staff, traffic across the country stopped at noon, and sirens were sounded from ships and trains.

Both Putin and Aliyev said Saturday that experts from Russia, Azerbaijan and Kazakhstan had begun probing the incident, and were launching inquiries in both Grozny and Aktau. Moscow has launched a criminal investigation into the crash.

Aliyev said Sunday that Azerbaijan was always ''in favor of a group of international experts'' investigating the matter, and had ''categorically refused'' Russia's suggestion that the Interstate Aviation Committee, which oversees civil aviation in the Commonwealth of Independent States, investigate the crash.