Ukraine's main mobile operator Kyivstar was on Thursday still recovering from the consequences of a cyberattack that Kyiv blamed on Russian hackers, which paralysed its networks two days ago.
Phone calls have mostly resumed but Kyivstar, which has over 24 million subscribers, said it would need a few days to re-establish other services.
"Region by region, we will carefully start restoring mobile Internet services," said Oleksandr Komarov, the head of Kyivstar, adding the process may take until the end of the week.
He said 99 percent of phone calls had been restored, while fixed internet access worked again for one million households.
Several subscribers living in Kyiv were only able to reconnect briefly on Thursday, before the signal disappeared again.
"Restoring a telecom network after a large-scale hacker attack is a complex process," Kyivstar said earlier.
"We continue to cooperate with the SBU (security service) and other state authorities to clarify all the details of the incident."
Komarov said hackers had likely been able to penetrate Kyivstar's security systems through the account of an employee of the company.
He added that the employee possibly "gave his password" to the hackers.
Since the start of the Russian invasion in February 2022, Kyivstar has repelled "around 500 more or less serious cyberattacks," Komarov added.