A Polish government official said today that Russia was behind a hacking attack that blocked users’ access to its online tax data system, as tensions between Warsaw and Moscow have escalated over the war in Ukraine.

Western officials say the Russian government is a world leader in cyberattacks and uses cyberespionage against foreign governments. Moscow has repeatedly denied conducting such operations.

“The Russians are responsible for yesterday’s attack, this must be clarified. We have information that makes it very likely that this was the adversary,” Janusz Siczynski, a government official in charge of digitization, told the Polsat News network.

The Russian embassy in Warsaw said in an emailed statement that it was “already used to the fact that in the West you can now blame Russia for anything without evidence. This is another such case in the familiar way of saying it is ‘very likely’.”

Siczynski said it was a DDoS (distributed denial of service) attack that blocked access to the website but did not leak taxpayer data.

“It is an attack that blocks access to the website but does not block security and does not put our data at risk,” he said.