Poland and the Baltic states on Monday asked Minsk to expel the Russian mercenary group Wagner, whose fighters have been stationed in Belarus since failing to overthrow the military leadership in Moscow.
"We have asked the regime [of Belarusian President Alexander] Lukashenko to immediately expel the Wagner group from Belarus," Polish Interior Minister Mariusz Kaminski said after meeting his counterparts from Lithuania, Latvia and Estonia.
Warsaw says thousands of Wagner fighters are currently stationed in Belarus, which borders Russia, Ukraine and Poland.
Lukashenko recently said he would keep some 10,000 Wagner troops in the country.
"Thousands, some of whom are criminals freed from Russian prisons in return for a promise to fight in Ukraine, are deeply demoralized and accused of crimes against humanity," Kaminski said.
"It's a major group, capable of anything," he said, warning Belarus that Poland would shut its frontier with the country in case of a "critical border incident."
The three countries also asked Belarus to "immediately send illegal migrants from the border region back to their home countries."
Warsaw has accused Belarus and Russia of orchestrating a new migration influx into the European Union in order to destabilize the region.
According to the Polish border guard, 19,000 migrants have tried to enter Poland from Belarus so far this year, compared to 16,000 during all of 2022.