A Polish soldier has died after being stabbed by a migrant on the country’s border with Belarus, Warsaw’s military said Thursday.

The soldier was involved in a clash with migrants attempting to cross Poland’s northeast border from Belarus on May 28, according to Polish media. He was stabbed in the chest through the border barrier.

Despite being treated at a hospital in the nearby city of Hajnówka, and then transported to a military hospital in Warsaw, “his life could not be saved,” the General Command of the Armed Forces said in a statement on X.

Prime Minister Donald Tusk paid tribute to the victim on X, writing: “The young soldier, Mateusz, gave his life defending the border of the Republic of Poland. The homeland and compatriots will not forget this sacrifice. I express my deepest sympathy to his loved ones.”

Mateusz has been officially identified only by his first name. His family have been informed.

Polish Defense Minister Władysław Kosiniak-Kamysz said in a post on Facebook that the soldier had “died while defending the Polish border” from “a bandit attack,” and called on his compatriots to “honour his memory!”

As Poles prepare to vote in the EU election on June 9, the soldier’s death could be used by the country’s right-wing and far-right parties, which have long campaigned on anti-immigration sentiment.

“A Polish soldier attacked with a knife on the Polish-Belarusian border by an illegal immigrant has died … Polish soldiers and border guards must have the right to defend themselves and shoot in self-defense and in defense of our border!” the leader of far-right party New Hope, Stanisław Tyszka, who is running for a seat in the European Parliament, said in a post on X Thursday.

Poland and the EU have previously accused Russia and Belarus of being behind an influx of migrants on the bloc’s eastern flank as a form of hybrid warfare.