Poland accused Belarus of staging an armed “intrusion” into its territory and said on November 3 that it had summoned the Belarusian charge d’affaires to protest “deliberate escalation” on the border.

The incident comes as thousands of migrants from the Middle East and Africa in recent months have attempted to illegally enter Poland and fellow EU members Latvia and Lithuania from Belarus.

The EU accuses Belarusian strongman Alyaksandr Lukashenka of flying in migrants and funneling them to the bloc’s borders to retaliate against Brussels for sanctions imposed over a sweeping crackdown since last year’s disputed presidential election.

Poland’s Foreign Ministry said “unidentified uniformed men armed with long guns” crossed the border overnight on November 1-2.

“Deputy Foreign Minister Piotr Wawrzyk forwarded an emphatic protest to the Belarusian side against the violation of the Polish state border, emphasizing that the actions taken by the Belarusian authorities in recent weeks have the increasingly evident hallmarks of a deliberate escalation,” the ministry said in a statement.

“He highlighted that Poland is determined to defend its borders and the external borders of the European Union,” it said, adding that Poland and its allies will oppose “illegal migration orchestrated by Minsk.”

Poland has imposed a state of emergency at the border, put up razor wire, and increased the number of soldiers and guards to stem the flow of migrants crossing from Belarus. Lawmakers last week also approved the building of a $407 million wall on its eastern border.

Last month, the Polish Border Guards said Belarusian forces fired shots — possibly blank ammunition — at its soldiers. In other cases, Poland accused Belarusian forces of destroying a razor-wire barrier on the border or encouraging migrants to do so.

Copyright (c) 2015. RFE/RL, Inc. Reprinted with the permission of Radio Free Europe/Radio Liberty, 1201 Connecticut Ave NW, Ste 400, Washington DC 20036.