"Due to the tragic events at the Polish–Belarusian border resulting in the death of a Polish soldier on duty, the Ministry of Foreign Affairs summoned Chargé d’Affaires of the Republic of Belarus Aleksei Ponkratenko," the Polish foreign ministry said in a statement.
It added that Ponkratenko was handed a protest note in which "Poland firmly calls on Belarus to stop provocations at the Polish–Belarusian border and orchestrating migration pressure."
"As the crime was committed on the Polish side of the border and given an ongoing prosecutorial investigation, the MFA also demands that the person responsible for murdering the Polish citizen be identified and surrendered," the Polish foreign ministry said.
A soldier of the 1st Armoured Brigade was stabbed by migrants trying to cross a fence on the Polish-Belarusian border at the end of last month. The military said the serviceman, named only as Mateusz, died on Thursday.
"Despite the help provided in the area of the criminal attack on the border with Belarus and the efforts of doctors, his life could not be saved," the Polish army said in a statement.
The defence ministry announced that all military units nationwide and Polish military contingents abroad would lower their national flags to half-mast to honour the dead soldier.
Polish Foreign Minister Radoslaw Sikorski said: "We demand that Belarusian authorities establish the identity of this murderer and hand him over to Polish authorities."
The Polish government has long accused Belarus of orchestrating the influx of migrants and sending them across the border.
Prime Minister Donald Tusk recently announced plans to reinforce the border and reinstate a 200-metre buffer zone.
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Source: IAR, PAP, Reuters, gov.pl