Hundreds of migrants sought to storm the border from Belarus into Poland on Monday, cutting razor wire fences and using branches to try and climb over them.
The siege escalated a crisis along the European Union’s eastern border that has been simmering for months.
Video footage appears to show a second incident involving small arms fire being heard by the border.
Poland’s interior ministry said it had rebuffed the illegal invasion and claimed the situation was under control.
The Defence Ministry posted a video showing an armed Polish officer using a chemical spray through a fence at men who were trying to cut the razor wire. Some migrants threw objects at police.
Video footage from Belarusian media showed people using long wooden poles or branches to try to get past a border fence as police helicopters circled overhead.
Migrants gather on the Belarusian-Polish border
BelTA
Defence Ministry video taken later showed the migrants settling in for the night by the border, having put up scores of tents and cooking meals.
“A coordinated attempt to massively enter the territory of the Republic of Poland by migrants used by Belarus for the hybrid attacks against Poland has just begun,” a spokesman for Poland’s security forces, Stanislaw Zaryn, said in a statement.
Noting that it is also Nato’s eastern border, Mr Zaryn stressed that the “large groups of migrants… are fully controlled by the Belarusian security services and army”.
He accused Belarusian President Alexander Lukashenko of acting to destabilise Poland and other EU countries to pressure the bloc into dropping its sanctions on Minsk.
Those sanctions were put into place after Belarus cracked down brutally on democracy protests.
Piotr Mueller, Poland’s government spokesperson, said 3,000 to 4,000 migrants were next to the Polish border on the Belarusian side.
Migrants gather on the Belarusian-Polish border
BelTA
Polish border officials said the border crossing in Kuznica, in the north east, will be closed early on Tuesday.
There was no way to independently verify what was happening. Journalists have limited ability to operate in Belarus and a state of emergency in Poland is keeping reporters and human rights workers out of the border area.
The massing of people at the border appeared to rev up the crisis that has being going on for months in which the autocratic regime of Belarus has encouraged migrants from the Middle East and elsewhere to illegally enter the European Union, at first through Lithuania and Latvia and now primarily through Poland.