Polish border forces on Wednesday said they were attacked with stones by migrants at the border with Belarus and responded by using water cannons against them.
The Border Guard agency posted video on Twitter showing a water cannon being directed across the border at a group of migrants in a makeshift camp in freezing temperatures.
Polish police said one officer was seriously injured. He was taken by ambulance to a hospital and it is likely his skull was fractured after being hit by an object.
The situation marks an escalation in a tense migration and political border crisis where the lives of thousands of migrants are at stake.
Poland's Defense Ministry said its soldiers and other border forces were attacked with stones and other objects.
The ministry also said that Belarusian forces tried to destroy fencing along the countries' common border, while the Interior Ministry posted video apparently showing migrants trying to tear down a fence.
There was no way to independently verify what was happening because a state of emergency in Poland is keeping reporters and human rights workers out of the border area. In Belarus journalists face severe restrictions on their ability to report as well, with only a few present at the border.
At one point Tuesday a Polish independent broadcaster, TVN24, was forced to rely on CNN in order to show a picture of the border not filtered through government authorities.
Poland's parliament is expected Tuesday to take up a legislative proposal that would regulate the ability of citizens to move in the area of the border with Belarus after the state of emergency ends at this end of this month.
The state of emergency was imposed at the beginning of September as a large number of migrants from the Middle East sought to cross into Poland from Belarus.
The border is also part of the European Union's eastern border, and the EU accuses the authoritarian regime of Belarusian President Alexander Lukashenko of fomenting a migration crisis in order to pressure the bloc.
The EU has been putting pressure on airlines to stop transporting Syrians, Iraqis and others to Belarus.
Meanwhile, the Iraqi government is urging its citizens trapped at the border to return home.
Some 200 Iraqi nationals who arrived in Belarus with the intention of crossing into the EU reached out to the Iraqi embassy in Russia and expressed a desire to return to their homeland, an embassy spokesman told the Interfax agency on Tuesday.
The spokesman added that an evacuation flight will take place on Thursday and all those wishing to return to Iraq are already in the Belarusian capital, Minsk, awaiting the flight. There were no issues with transporting the migrants from the border to Minsk, the diplomat told Interfax, and Belarusian authorities have provided all the necessary assistance.