The move by Poland to shut a border crossing between the two nations was denounced as “catastrophic” by Belarus on Friday, warning that it could result in a collapse on both sides of the border.

Poland announced on Thursday that it would shut down a crucial border crossing into Belarus at Bobrowniki beginning at noon (1100 GMT) on Friday, escalating already tense relations between the two nations to a new low. Poland cited security concerns as the reason for the closure.

Poland has been a key refuge for opponents of Belarus President Alexander Lukashenko and Warsaw has become one of Kyiv’s staunchest supporters since Belarus’ main ally Russia invaded Ukraine in February 2022.

The Belarus government criticized the border decision on Thursday, but went further in a statement on Friday, calling the move irrational and dangerous.

“The actions of the Polish authorities could lead to a collapse on both sides of the border,” the country’s border committee said in a statement shared on social media.

After the closure comes into force, only two of six major land crossing points along the two countries’ 400-km (250- mile) border will be open, the border force said.

“With the closure of another Polish checkpoint, the situation will become catastrophic,” it added, pointing to existing long lines at border crossings. “The load on the remaining two checkpoints will critically increase.”

Minsk also said it believed the decision was purposefully designed to “further aggravate the situation at the border and limit citizens’ travel”.

Polish Prime Minister Mateusz Morawiecki said that Poland might close further border crossings.

“We are not excluding closing other border crossings with Belarus,” he told a news conference in Brussels. “The reason for this is that there are growing tensions with Belarus and they are being instrumentalised by the Russians and the Kremlin.”

Relations were further strained on Wednesday when a Belarusian court sentenced a journalist of Polish origin to eight years in prison in a trial Warsaw said was politically motivated.

Thousands of people of Polish origin live in Belarus given that the west of the country was Polish territory until borders were redrawn after World War Two.