Poland plans to build a fence to stop migrants from Belarus and fend off what Baltic leaders say is an effort to destabilise them.
The prime ministers of four EU states have accused Belarus of carrying out a “hybrid attack” on their borders by allegedly triggering a flow of migrants.
They said Minsk was behind a “planned and systemically organised” effort to weaken the EU, which has imposed sanctions on Belarus over a crackdown on opposition.
The crisis was initially concentrated at Belarus’s border with Lithuania, but has spread to Poland and Latvia.
Poland said 2,100 people tried to enter its territory from Belarus in August, prompting Warsaw to send 900 soldiers to the border.
Defence Minister Mariusz Blaszczak said a 2.5-metre fence would be built on the border, which will be reinforced with 150 kilometres of razor wire.
He said it would be modelled on a fence Hungary built on its border to keep out migrants from non-EU member Serbia.
“We are dealing with an attack on Poland. It is an attempt to trigger a migration crisis,” Mr Blaszczak said.
“We will not allow the creation of a route for the transfer of migrants via Poland to the European Union.”
The leaders of Poland, Lithuania, Latvia and Estonia want the UN’s refugee agency to take up the matter with Belarusian authorities.
“Weaponising refugees and immigrants threatens the regional security of the European Union and constitutes a grave breach of human rights,” they said.
“We also believe that it is high time to bring the issue of abusing migrants … to the attention of the UN, including the United Nations Security Council.”
UNHCR spokeswoman Shabia Mantoo said the refugee agency had been closely following the situation.
“We have been very concerned by developments at the borders resulting in people being stranded for days,” she said.
The migrants are mostly from Afghanistan and Iraq. Flights from Baghdad were suspended after claims that Belarus was shuttling people to the border.
Activists say that a group of 30 people stuck on Poland’s border with Belarus include Afghans who require medical attention.
Poland has refused to let them apply for asylum, insisting they are on Belarusian territory, but offered to send humanitarian aid to the group.
It offered to provide food and medicine, as well as tents, beds, sleeping bags, blankets and pyjamas, the Polish Foreign Ministry said.
At the border guard headquarters in Warsaw, activists chained themselves to a fence and put barbed wire on the gates.
Belarusian President Alexander Lukashenko has criticised Polish authorities for allegedly using force to push migrants back into Belarus.
“They caught 50 people heading to Germany … and pushed them to the border with Belarus by firing shots in the air,” Mr Lukashenko said.
The EU placed sanctions on Belarus after an election last year that sparked protests and led to arrests of opposition figures.
Further sanctions were imposed after Belarusian authorities arrested a journalist whose plane was forced to land in Minsk this year.