Belarus and Poland are pushing refugees back and forth across their border and leaving them with little if any food, clean water or shelter, the United Nations Human Rights office said on Tuesday, urging both countries to address "this appalling situation."

Refugees and migrants interviewed by a U.N. human rights team on a Nov. 29 to Dec. 3 trip to Poland said they had suffered violence or threats in Belarus and been left hungry and cold, a spokesperson for the U.N. Human Rights office 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.

Most said that, while in Belarus, they had been beaten or threatened by security forces, who some refugees said had also demanded "extortionate sums" for food and water and forced them to cross the border.

Thousands of migrants are stuck on the European Union's eastern frontier.

Poland and the EU accuse Belarusian President Alexander Lukashenko of encouraging the migrants to travel to Belarus and cross the border illegally as revenge for sanctions imposed on Minsk over human rights abuse.

Belarus denies this and says the EU is to blame for the humanitarian crisis on the border.

Stanislaw Zaryn, a spokesperson for Poland's special services, said his country's actions were legitimate and aimed 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," he said.

Throssell said many migrants and refugees interviewed by the U.N. team had crossed the border several times in both directions due to "recurring practices by the two countries of pushing people up to or across the border."

Some of them hid from security forces for weeks in the forest along the border, with one making 26 attempts to cross from Belarus to Poland.

The U.N. Human Rights office, which said Belarus had not accepted its request to visit, urged both countries to "ensure that refugees' and migrants' human rights are at the center of their actions."