Belarus has reportedly been encouraging migrants to illegally enter the European Union through Poland, with the bloc saying this is being done in revenge for Western sanctions on Minsk over human rights abuses.
A march through the Polish capital to mark Independence Day was led by far-right groups calling for strong borders.
It comes as the situation on the border worsens, with migrants facing freezing conditions. Already seven deaths have been reported on the Poland side of the border - with reports of more deaths in Belarus.
March leader Robert Bakiewicz said all Poles should back those protecting the eastern border, which has been lined with some thousands of Polish troops, along with police and guards.
“Today there are not only internal disputes. Today there are also external disputes. Today there is an attack on the Polish border,” he said in a speech.
Polish authorities have accused Belarus of trying to trigger a major confrontation by deliberately directing thousands of people - mainly from the Middle East and Asia- to the border in recent months.
The Belarusian Defense Ministry has accused Poland of an “unprecedented” military build-up there.
On Thursday, the ministry said migrants made a number of attempts to cross the border since Wednesday, as they have all week.
Near the village of Bialowieza, where a group of a few hundred migrants threw debris across the fence at Polish troops and then tried to destroy it, shots were fired in the air to deter them.
Shots also were fired in the air near the village of Szudzialowo after migrants attacked a soldier, according to the ministry. The soldier did not suffer injuries from the incident.
“He was hit with a branch on the chest. He fired two warning shots into the air,” the ministry said. Since the start of the year, there have been 33,000 attempts to cross the border illegally, with 17,000 in October alone, the border guard service said.
Poland said on Monday that seven migrants had been found dead on its side of the border, with reports of more deaths in Belarus.
Charities say the migrants face freezing weather conditions as the cold Polish winter kicks in and a lack of food and medical attention could put even more at risk.
Since the summer, Poland has been under increasing pressure of migrants from the Middle East and Africa trying to cross into the EU. Poland has sought to block the attempts or send those they catch back into Belarus.
Warsaw and the EU say it’s an organised action by the Belarusian government aimed at destabilising the bloc in retaliation for Western sanctions.
The EU, the US and Britain imposed sanctions on Belarus after President Alexander Lukashenko unleashed a violent crackdown on mass protests following a disputed election last year.
The long-time leader of Belarus won re-election for a sixth time in 2020 with 80% of the vote, in a ballot deemed “neither free nor fair” by the EU, sparking international outrage.
Lukashenko has defied opposition calls to resign.