Stone-throwing migrants trying to cross the border from Belarus were met with tear gas and water cannons by Polish forces.
"Migrants threw rocks at our soldiers and officers and are attempting to demolish the fence and cross into Poland," Poland's defense ministry said on Tuesday, tweeting a video of potential border confrontations.
"Our forces used tear gas to disperse the refugees."
During the clashes, a Polish cop was critically hurt, with a possible skull fracture, while stun grenades and tear gas canisters were thrown back at officers, according to police.
The deployment of tear gas and water cannons by Poland on refugees was criticised by Russia, with Foreign Minister Sergey Lavrov calling it "completely reprehensible."
According to Polish border guards, up to 4,000 refugees are reportedly camped along the Poland-Belarus border in increasingly dangerous conditions and frigid weather.
"We cannot allow this so-called problem to escalate into a fierce conflict," Lukashenko said Tuesday during a government meeting.
According to state news agency Belta, he continued, "The essential issue today is to defend our country and our people, and not to allow conflicts."
On Monday, Belarusian President Alexander Lukashenko met with German Chancellor Angela Merkel to discuss the problem, and the two agreed that the deadlock should be resolved.
According to Merkel's office, the two discussed sending humanitarian aid to the migrants, who include many children.
"We were all of the same mind that escalation was unnecessary, neither for the EU nor for Belarus," Lukashenko added.
But he added he and Merkel had "differing" views on how the refugees arrived in Belarus, with the West accusing Minsk of bringing them there as retaliation for sanctions.
Existing penalties on Lukashenko's regime will be broadened to cover inpiduals or firms proven to have supported border crossings, EU foreign ministers agreed on Monday.