The United States authorities on Friday said that Russian air defence systems may have led to the Azerbaijan Airlines crash near Kazakhstan’s Aktau city, AP reported.

This came hours after Azerbaijani Transport Minister Rashad Nabiyev said that the passenger aircraft was subjected to “external interference” and damaged inside and outside as it tried to land in Russia’s Chechnya region, BBC reported.

Later on Saturday, Russian President Vladimir Putin extended an apology to Azerbaijan's President Ilham Aliyev for the “tragic incident” in Russian airspace and said that Russian air defence systems had been activated in response to Ukrainian drones, Reuters reported.

“At that time, [the towns of] Grozny, Mozdok and Vladikavkaz were being attacked by Ukrainian unmanned aerial vehicles, and Russian air defence systems repelled these attacks," the Kremlin said in a statement.

At least 38 persons died after the passenger aircraft operated by Azerbaijan Airlines crashed on Wednesday. The plane was carrying 62 passengers and five crew members. All 29 survivors were injured.

It was travelling from the Azerbaijani capital of Baku to the Russian city of Grozny but had been rerouted midway.

On Friday, White House Spokesperson John Kirby told reporters that the United States had “seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defence systems”, AP reported.

Kirby, however, refused to elaborate on the matter, saying that the investigation was on.

Earlier in the day, Nabiyev said that preliminary conclusions by experts pointed to an external impact. “All [the survivors] without exception stated they heard three blast sounds when the aircraft was above Grozny,” BBC quoted him as saying.

He added: “The type of weapon used in the impact will be determined during the probe.”

The Azerbaijani prosecutor general’s office also said that investigators from the country were working in Grozny as part of its probe into the crash, AP reported.

On its part, Russian authorities said that the situation in Grozny was “very complicated” and a closed-skies protocol had been put in place at the time of the crash, BBC reported.

“Ukrainian combat drones were launching terrorist attacks on civilian infrastructure in the cities of Grozny and Vladikavkaz,” Dmitry Yadrov, the head of Russia’s civil aviation authority Rosaviatsia, was quoted as saying on Friday.

The crash came amid Russia’s war on Ukraine, the deadliest conflict in Europe since the Second World War.

As per reports, Ukrainian drones have previously attacked Grozny and other areas in the region.

Yadrov also noted that the captain of the aircraft that crashed had made two unsuccessful attempts to land. When he failed to do so, he was offered other airports but decided to fly to Aktau, Yadrov added.

On Friday, Azerbaijan Airlines blamed the crash on unspecified “physical and technical interference”, AP reported. It also announced the suspension of flights to several Russian airports.