A Polish government official said on Wednesday that Russia was behind a hacking attack that blocked users’ access to the online tax filing system, as tensions between Warsaw and Moscow run high due to the war in Ukraine.

“Russians are responsible for yesterday’s attack, it must be made clear. We have information that makes it very likely that this was the adversary,” Reuters reports Janusz Cieszynski, a government official responsible for digitalisation, told broadcaster Polsat News.

The Russian embassy in Warsaw did not immediately reply to an emailed request from Reuters for comment.

Cieszynski said the attack consisted of distributed denial of service which resulted in blocking access to the website, but taxpayers’ data were not leaked.

“This is an attack that blocks access to the site, but does not block security and put our data at risk.”