The UN human rights office says that Belarus and Poland are forcing migrants and refugees back and forth across their border, often leaving them cold and with no food, clean water, or safe shelter.
The UN agency on December 21 called on the two countries to address the "appalling situation" and relieve the "dire conditions" for those along the frontier, saying some of them are being threatened or beaten by Belarusian security forces.
The European Union accuses Belarusian strongman Alyaksandr Lukashenka of flying in migrants and funneling them to the borders of member states Poland, Latvia, and Lithuania to retaliate for sanctions the bloc imposed over a sweeping crackdown since last year's disputed presidential election.
Refugees and migrants interviewed by a UN human rights team visiting Poland in late November and early December said they had suffered violence or threats in Belarus and been left hungry and cold, a UN spokeswoman said.
"Those interviewed described dire conditions on both sides of the border, with no or limited access to food, clean water, and shelter, often amid freezing temperatures," Elizabeth Throssell told reporters.
She added that most of them said that while in Belarus, they had been beaten or threatened by security forces.
"Several interviewees said Belarusian security forces had demanded extortionate sums for food and water," Throssell said.
Belarus has denied it has caused a border crisis and blames the EU for the humanitarian disaster along its borders.
The UN human rights office said both countries had prevented access to the border area for its staff. While in Poland, the UN team interviewed people who had crossed the border over the past several months.
Belarus has not allowed its teams to visit the country, the UN said.
A spokesman for Poland's special services said his country was acting within the law and that its actions were undertaken to protect the country's borders.
"The migration route, controlled and organized by the Belarusian services, is only a tool used by the regime in Minsk," Stanislaw Zaryn said.
Poland has taken steps in response to the migrant crisis, including building a barbed-wire fence and massing thousands of soldiers along its 400-kilometer border with Belarus.
Throssell said many migrants and refugees had crossed the border several times in both directions because of "practices by the two countries of pushing people up to or across the border."