Russian state-owned flagship carrier Aeroflot suffered a mass IT outage Monday following a cyberattack, Russia's prosecutor's office said, forcing the airline to cancel more than 100 flights and delay others.

Footage shared on social media showed hundreds of delayed passengers crowding Moscow's Sheremetyevo airport, where Aeroflot is based. The outage also disrupted flights operated by Aeroflot's subsidiaries, Rossiya and Pobeda.

While most of the flights affected were domestic, the disruption also led to cancellations for some international flights to Belarus, Armenia and Uzbekistan.

In a statement released early Monday, Aeroflot warned passengers that the company's IT system was experiencing unspecified difficulties and that disruption could follow.

Russia's Prosecutor's Office later confirmed that a cyberattack had caused the outage and that it had opened a criminal investigation.

Kremlin spokesperson Dmitry Peskov called reports of the attack "quite alarming," adding that "the hacker threat is a threat that remains for all large companies providing services to the general public."

Ukrainian hacker group Silent Crow and Belarusian hacker activist group the Belarus Cyber-Partisans, which opposes the rule of Belarusian leader Alexander Lukashenko, claimed responsibility for the attack.

The group claimed it had accessed Aeroflot's corporate network for a year, copying customer and internal data, including audio recordings of phone calls, data from the company's own surveillance on employees and other intercepted communications.

"All of these resources are now inaccessible or destroyed and restoring them will possibly require tens of millions of dollars. The damage is strategic," the channel purporting to the Silent Crow group wrote on Telegram. There was no way to independently verify its claims.

The same channel also shared screenshots that appeared to show Aeroflot's internal IT systems and insinuated that Silent Crow could begin sharing the data it had seized in the coming days.

"The personal data of all Russians who have ever flown with Aeroflot have now also gone on a trip - albeit without luggage and to the same destination," it said.

Russia's airports have repeatedly faced mass delays over the summer as a result of Ukrainian drone attacks, with flights grounded amid safety concerns.