Air raid alert systems in some parts of Ukraine, including Kyiv Oblast, Sumy, and Dnipro, face technical issues due to the hack on telecommunications company Kyivstar, regional authorities reported on Dec. 12.
The news comes after a "massive" hacker attack was reported on Dec. 12 by Kyivstar, causing widespread internet and network outages. Monobank, one of Ukraine's largest banks, also reported a hack.
Kyivstar is Ukraine's leading phone services provider, with over 24 million mobile customers. The attack caused a large-scale technical failure that resulted in the loss of mobile connection and internet access "in parts of (Kyivstar's) subscriber base."
The air raid alert system in parts of Kyiv Oblast is not functioning due to issues with the Kyivstar network , Governor Ruslan Kravchenko said at around 4 p.m. on Dec. 12.
According to Kravchenko, the air raid alert is not functioning in some parts of Kyiv Oblast, including Bucha, Irpin, Vyshneve, and parts of Boryspil.
In another 75 settlements, the system was down but has been backed up by another warning system, according to Kravchenko. The air raid alert system in Kyiv itself is unaffected by the hack, Kyiv city authorities said earlier in the afternoon.
Emergency service workers and the police will use loudspeakers to signal the alert in case an area where the alert is not functioning is under threat of an attack, Kravchenko said.
The city of Sumy will sound the alert in the same way "while the specialists of the mobile operator eliminate technical malfunctions," the local military administration said.
The air raid system is "temporarily" not working due to ongoing issues with the operator Kyivstar, according to the military administration.
Issues with the air raid alert were also reported in Dnipro, the local authorities said on the afternoon of Dec. 12.
"Due to a hacker attack on the mobile operator "Kyivstar" in Dnipro, the local air alert system is not working," Dnipro city council said.
The authorities advised residents to listen out for the alert on local radio stations and Telegram channels.
Kharkiv Regional Military Administration also reported issues with the air raid alert system, but did not explicitly point to the Kyivstar hack as the reason.
The authorities said the system was not fully functioning due to technical repairs being carried out and advised residents to use the official mobile application, rather than rely on the sirens.
Kyivstar CEO Oleksandr Komarov released a video message at around 4 p.m. local time, and said that the company was still working to restore the network.
It was "not completely clear" when the issue would be resolved, however. "The war with Russia has many dimensions, and one of them is in cyberspace," Komarov said.
The Security Service of Ukraine (SBU) announced it has opened criminal proceedings concerning the hack.