Poland’s Prime Minister Donald Tusk has said that his centrist political party has been the target of a cyberattack.

In a post on social media platform X, Tusk said that available evidence suggested the attack had “eastern” origins, thought to be a reference to Russia or Belarus.

Tusk said his Civic Platform party’s computer system was targeted, ahead of next month’s presidential election.

“Foreign interference in elections begins,” Tusk said in his online post.

Jan Grabiec, the head of Tusk’s office, told the Polish state news agency PAP that the cyberattack consisted of an attempt to take control of computers of employees of the Civic Platform office and the election staff over about a 12 hours on Wednesday.

Asked if Tusk was pointing the finger at Russia or Belarus, Grabiec said that would be for Poland’s secret services to comment on, but that in past cases Belarusians have infiltrated Poland’s systems on behalf of Russian intelligence services.

Poland is weeks away from the first round of a presidential election, scheduled for 18 May.

The frontrunner is the Civic Platform candidate, Warsaw Mayor Rafał Trzaskowski, who like Tusk is a pro-European Union centrist. He has been polling at around 35%.

His main contenders include a conservative backed by the Law and Justice party, Karol Nawrocki, who is second in most polls at a bit over 20%, and a co-leader of the far-right Confederation party, Sławomir Mentzen, who has been polling around 20%.

If no candidate wins outright with at least 50% of the vote, a runoff will be held 1 June.