Subscribers of Ukraine's largest mobile phone operator report that service is gradually being restored after a cyberattack that was claimed by a Russian hacking group.
Kyivstar said on December 13 that its specialists were working on restoring services, saying this may occur gradually but it is doing everything it can to complete the work as soon as possible.
"Friends, the enemy's strategy is to sow panic. Let's not let him succeed!" Kyivstar said on Facebook. "As we reported before, the subscriber information and personal data are safe. The systems in which this data is stored have not been affected by a hacking attack."
Ukraine's Security Service (SBU) said earlier that its cyber-specialists were working to repair the network in cooperation with other government agencies. The SBU also said it opened a criminal proceeding into the hack.
"One of the versions currently being investigated by the SBU investigators is that the special services of the Russian Federation may be behind this hacker attack," RFE/RL was told by the SBU.
The SBU said Internet for households should be completely restored sometime on December 13, followed by the partial relaunch of mobile phone and Internet services. The SBU said the slow pace of the repair work was due to the extensive damage suffered by Kyivstar's digital infrastructure.
The attack on Kyivstar, which has around 24 million mobile subscribers and more than 1.1 million home Internet users, knocked out services, damaged IT infrastructure, and silenced air-raid-alert systems in some parts of Ukraine.
A group of activist hackers called Solntsepyok said on Telegram that it carried out the cyberattack.
Ukraine's State Service of Special Communications and Information Protectorate (SSSCIP) said in a statement that responsibility for the attack has been claimed by a Russian group whose activities are associated with Russia's GRU military intelligence agency.
"This once again confirms Russia's use of cyberspace as one of the domains of the war against Ukraine," it said, without naming the group that has claimed responsibility.
Earlier this year, the SSSCIP identified Solntsepyok as a front for a Russian hacking group dubbed Sandworm, which has been previously linked to the GRU.
Sandworm has been tracked by cybersecurity researchers as having been responsible for cyberattacks on Ukraine's energy sector.