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Kyivstar continues working to fully restore services after suffering a major hacker attack late last week that disrupted networks across large parts of western and southern Ukraine.

In a statement, the leading mobile operator explained its network is still in the stabilization process after the large-scale cyber incident, meaning some subscribers may sporadically experience service difficulties in the short term as systems are brought back online and secured.

On Wednesday morning, in a number of cities in the west and south of Ukraine, difficulties arose with voice communication and the operation of the My Kyivstar mobile application.

"The company's specialists are working to restore services. We are doing everything possible to eliminate technical problems as soon as possible," the message says.

The company promises to inform subscribers about compensations soon.

As of Tuesday, 99% of Kyivstar base stations are operational, the company's spokeswoman Iryna Lelichenko told LIGA.net. High-speed mobile internet has already been restored in the subways of Kyiv and Kharkiv.