Two large groups of migrants have reportedly broken through the border from Belarus to Poland.
Several dozen people managed to destroy fences close to the villages of Krynki and Bialowieza and to cross the border, Polish news agency PAP reported late Tuesday, citing the Bialystok local radio station.
The broadcaster cited a border force spokeswoman saying that in both cases the fences and barriers were violently torn down.
Some migrants were taken back to Belarus, while others managed to flee, she said.
There were hundreds of people on the Belarusian side.
Poland is refusing to let the migrants onto its territory and has sent hundreds of reinforcements to the border in recent weeks, as well as erecting a barbed wire fence, in an effort to stop any attempts by migrants to break through.
Belarusian leader Alexander Lukashenko demanded Tuesday that they be allowed through into Poland.
He said in an interview they mainly wanted to settle in Germany, not Poland.
The European Union has accused Minsk of helping migrants trying to reach the bloc's external borders in Poland, Latvia and Lithuania in retaliation for Western sanctions on Belarus for political repression.
Lukashenko, who has been dubbed "Europe's last dictator," has denied deliberately flying people in from nations in crisis like Syria, Afghanistan, Libya and Iraq and then moving them towards the EU border.
The EU is currently planning fresh sanctions against Belarus, principally to target state airline Belavia for allegedly transporting migrants to Belarus.