The largest operator of mobile telephony in Ukraine, Kyivstar denounced an act of “war” by Russia following the major cyber attack that today paralyzed its network and “partially destroyed” its IT infrastructure.

“This is a war, which is being waged not only on the battlefield, but also in the world of virtual networks, and unfortunately, we have been affected by this war,” said the director consultant of the Kyivstar group, Oleksandr Komarovspeaking on state-run Ukrainian television.

“(The attack) caused severe damage to the IT infrastructure, limited access, we could not counter it at the level of virtual networks, so we disrupted Kyivstar’s services to limit the enemy’s access,” Komarov said.

“This morning we were the target of a major hacker attack. It caused a technical failure that made mobile phone services and Internet access temporarily unavailable,” Kyivstar said in a statement posted on Facebook earlier.

The Ukrainian security service SBU announced for its part that cyberattack on Kyivstar may be a Russian intelligence operation.

“One of the versions currently being investigated by the SBU is that Russian special services may be behind this cyber attack,” the SBU said in a written statement to Reuters.

Kyivstar’s network has more than 24 million subscribers.

The outage affected a number of services across the country.

Ukraine’s largest bank, Privatbank, reported that some of its ATMs and terminals were affected by the cyber attackaccording to the Hromadske public television website.

In Sumi (northeast), air raid warning sirens stopped working, the military administration of this city announced on Telegram. In Lviv, western Ukraine, the outage affected the operation of the public lighting system, according to the city council.

One of the major Ukrainian banks, Monobank, said it was the target of a “massive DDoS (distributed denial of service) attack”.