Poland is building a 2.5-metre-high fence on its border with its eastern neighbour Belarus because of the large number of migrants entering the country illegally.
More soldiers are to reinforce security on the border, Defence Minister Mariusz Blaszczak wrote on Twitter on Monday.
Nine hundred soldiers are already deployed along the 418-kilometre-long border with Belarus.
Belarusian ruler Alexander Lukashenko announced at the end of May that Minsk would no longer prevent migrants that arrive on its soil from traveling on to the EU, as a reaction to tighter Western sanctions.
Since then, Lithuania in particular has been struggling with a rush of migrants from the Middle East across the border with Belarus, and recently pressure on Poland has also increased.
On Monday, Lukashenko accused the Poles of instigating a conflict at the border and sending migrants back to Belarusian territory.
"The Poles captured 50 people on Polish territory who ... wanted to go to Germany, where Mother [German Chancellor Angela] Merkel had called them," he said, according to the Belta agency. Afterwards, he said, the Poles drove this group to the Belarusian side of the border under threat of armed force.
According to the Polish border guard force, a group of 24 refugees had been holding out for days near the village of Usnarz Gorny near the border with Belarus.
According to the PAP news agency, they are Afghans.
Polish border guards had surrounded the refugees and blocked access with vehicles, while armed security forces could also be seen on the Belarusian side.