Several Ukrainian government websites and the websites of some Ukrainian banks were offline on February 23 in what the government said was another apparent cyberattack.
The websites of the parliament, the cabinet, and the Ministry of Reintegration of the Occupied Territories were among those that were inaccessible.
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Ukraine’s state cybersecurity agency said the attack temporarily disabled the websites, adding that attacks in general have sharply escalated in the past week.
The agency blamed the attack on Russian actors, saying they are "no longer even trying" to hide their identity.
The government said it was the start of a distributed denial of service (DDoS) attack -- a type of attack that overwhelms websites by sending a large number of requests at once.
"At about 4 p.m., another mass DDoS attack on our state began. We have relevant data from a number of banks," said Minister of Digital Transformation Mykhailo Fedorov.
The websites were not accessible or only barely functioning. Security measures taken after previous cyberattacks, including one last week, appeared to prevent the attack from hitting other government sites.
The United States is in touch with Ukrainian authorities about the country’s cybersecurity needs, White House spokeswoman Jen Psaki said.
"We're going to move with urgency to assess the nature and extent of [the cyberattack], what steps need to be taken, and therefore a response," she said.
Ukrainian authorities said this week they had seen online warnings that hackers were preparing to launch major attacks on government agencies, banks, and the defense sector.
The online networks of the Defense Ministry and two banks were overwhelmed last week in the most recent cyberattack. Ukraine blamed that DDoS attack on Russia. Moscow has denied any involvement.
Fears of a Russian invasion, which have been growing for weeks, intensified on February 22 when the Kremlin recognized the independence of areas controlled by Russia-backed separatists in eastern Ukraine.
Russian President Vladimir Putin has also requested and received approval for the deployment of troops into eastern Ukraine, although he said he had not yet decided to order the move.