Poland faced “many attempts” to breach the border with Belarus overnight but now has 15,000 troops to repel them, the defence minister has said.
Several thousand migrants have become stranded at the border at the centre of an escalating international row.
For months, the European Union (EU), and now National Atlantic Treaty Organisation (NATO) and the US, have accused Belarus’s authoritarian leader of provoking a renewed migrant crisis in Europe.
Ever-increasing numbers have headed to Belarus’s borders with the EU.
Alexander Lukashenko, who won a largely discredited election last year, denies luring would-be migrants – mostly from the Middle East – to the EU’s borders in retaliation to sanctions imposed since he brutally cracked down on protesters and opponents.
The situation has come to a head this week with repeated attempts to tear down the razor-wire fence erected on Poland’s eastern frontier.
“It wasn’t a calm night. Indeed, there were many attempts to breach the Polish border,” Defence Minister Mariusz Blaszczak told Polish radio.
The police spoke of two separate incidents involving groups of about 50 people.
Poland and Belarus have accused each other of violence towards migrants camped near the fence. Those claims are difficult to verify as a BBC team and other journalists have been barred from the area because of a local Polish state of emergency.
However, the defence ministry in Warsaw tweeted a video alleging that a Belarusian soldier fired a shot to intimidate the migrants camped near the fence.
Overnight temperatures at the border have fallen below freezing and some of the people stranded there have warned they are running out of food and water.
Aid workers complain that Poland’s state of emergency means they are unable to enter the affected area: “For us it is heart-breaking. We are here, near the border and we cannot enter the zone and help people. We can only help those who manage to cross the border and make it out of the restricted area,” Ania Chmielewska told the BBC.
The defence minister said earlier attempts had focused on the area around a major border crossing at Kuznica but latest efforts are more spread out. -BBC