Two of the injured had to be hospitalised, Deputy Defence Minister Wojciech Skurkiewicz said.
The news came after Poland's Border Guard agency requested that Belarus remove migrants gathered near the Kuźnica checkpoint at the shared border by the end of this week, state news agency PAP reported.
The border agency warned that if the migrants were not taken away by Sunday, November 21, Poland would suspend all cargo train traffic going through Kuźnica.
The Border Guard's chief, Tomasz Praga, said that "as long as multiple groups of migrants, who are hostile towards Polish border personnel, remain near the crossing, many unexpected and dangerous situations may develop, including a railway disaster."
The request was authorised by Poland's Interior Minister Mariusz Kamiński and shared on Twitter.
It came after violent scenes in Kuźnica on Tuesday when large groups of migrants, amassed on the Belarusian side of the border, pelted Polish forces with rocks and stun grenades, according to officials.
Meanwhile, the main makeshift migrant camp near Kuźnica has been cleared by Belarus, but migrants tried to breach the Polish border in other places overnight, the country's police chief told Polish Radio on Friday.
Polish police tweeted an aerial video of the deserted camp near Kuźnica, with extinguished fires and remnants of stick huts left behind, public broadcaster Polish Radio's IAR news agency reported.
Poland's Border Guard said on Friday it had recorded 255 illegal attempts to cross from Belarus over the past 24 hours. Since the start of the year, over 35,000 such attempts have been recorded, including 6,300 this month alone, the agency's data showed.
Stanisław Żaryn, the spokesman for Poland's security services, told Polish Radio on Friday that both the migrants and the Belarusian officials escorting them were becoming increasingly aggressive toward Polish border forces.
Stanisław Żaryn. Photo: Polish Radio
Two latest large-scale attempts to cross into Poland happened late on Thursday, the Border Guard reported.
First, some 500 migrants tried to force their way through near the village of Dubicze Cerkiewne.
"These people were aggressive, throwing stones and tree branches," the agency's spokeswoman, Anna Michalska, told reporters.
The migrants were being assisted by Belarusian officials, who used lasers and tear gas, "injuring four Polish soldiers," she said.
After Polish forces repelled the attack, "Belarusian trucks took some of the migrants away," while others "could still be encamped" in the nearby woods, Michalska added.
Then, at around 10 p.m. on Thursday, some 50 immigrants broke into Polish territory near the village of Mielniki, the Border Guard reported.
But "this group was detained and turned back, with the exception of an Iraqi family, a man, his pregnant wife and three children, who received first aid at our premises," Michalska said.
She added that the Iraqi family had been taken to a guarded facility where they could apply for international protection. The father of the family said he would like to stay and work in Poland, Michalska told the media.
Anna Michalska, spokeswoman for the Polish Border Guard. Photo: PAP/Wojciech Olkuśnik
The months-long migrant crisis on the Polish-Belarusian border has escalated in recent days, with Poland, the European Union and its member states, as well as NATO and the United States accusing Belarusian leader Alexander Lukashenko of orchestrating the standoff in retaliation for Western sanctions against his regime.
Lukashenko has denied luring vulnerable people, including Kurds from the Middle East, with the false promise of easy access to the EU and sending them across the bloc's border.
Polish lawmakers on Wednesday backed a government plan to strengthen the country's borders amid the migrant crisis on its frontier with Belarus.
Prosecutors this week opened an investigation into an attack on Polish border guards, police officers and soldiers staged from across the border with Belarus by rock-throwing assailants, Poland's police chief told reporters.
Source: IAR, PAP