Ukraine mobile network Kyivstar hit by 'cyber-attack'

Kyivstar is said to be working on additional security measures to prevent future incidents

Ukraine's main mobile network, Kyivstar, says it's been the target of a "powerful hacker attack".

Customers have been left without phone or internet access, while one city's air raid sirens stopped working. Kyivstar's chief executive implied Russia could be responsible.

Ukraine's security services are investigating. Moscow hasn't commented.

The Kyivstar network is estimated to have some 24 million mobile customers and a million home internet users.

Reports emerged on Tuesday morning that people and businesses had lost mobile and internet signal.

Air raid sirens in the north-eastern city of Sumy also malfunctioned as a result of the outage.

Military authorities in the area announced they would send out police and emergency vehicles to alert residents of any incoming missile or drone strikes.

Ukraine's largest bank, PrivatBank, said some cash machines were not working and might be "unstable" or "have no connection".

An investigation has been opened by the Security Service of Ukraine (SBU).

"One of the versions currently being investigated by SBU investigators is that the Russian special services may be behind this hacker attack," SBU said in a statement.

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Kyivstar said earlier it had called in law enforcement agencies because of the "illegal interference".

The company's general director, Oleksandr Komarov, also appeared to suggest Russian actors could be to blame.

"The war with Russia has many dimensions and one of them is in cyberspace," he said.

"We are working to restore communication as soon as possible," he added and promised compensation for affected customers.

The operator said no-one's personal data had been compromised.

Russia launched a full-scale invasion of Ukraine in February 2022, with the war now well into its second year.

Dutch-domiciled parent company Veon said it would work with Kyivstar on "additional security measures" to prevent similar incidents in future.

Separately, Ukraine's military intelligence claimed to have carried out a cyber-attack on Russia's federal tax system in recent days.

"During the special operation, military intelligence of Ukraine managed to break into one of the well-protected key central servers of the federal tax service," read a statement on Telegram.

It said Russian efforts to restore services were now into their fourth day.