Poland has recalled its ambassador from neighbouring Belarus amid escalating tension between the Polish government and Belarus' president.
The Union of Poles has been targeted by Belarus police
President Alexander Lukashenko has accused the Polish minority in Belarus of plotting to overthrow him.
On Wednesday, Belarussian police raided the headquarters of an organisation representing ethnic Poles in Belarus and briefly detained its leader.
Each country has expelled the other's diplomats in recent months.
About 400,000 ethnic Poles live in Belarus, in areas that were part of Poland until World War II.
Mr Lukashenko has accused Poland of interfering in Belarussian affairs and seeking to provoke mass protests against his government.
Poland says Mr Lukashenko's government is persecuting the Polish community.
Fears of backlash
Riot police with guns and dogs raided the Union of Poles headquarters in the western town of Grodno, about 280 km (175 miles) west of the capital, Minsk, on Wednesday, detaining those inside for several hours.
Mr Lukashenko has criticised the recently elected leadership of the association, saying it is illegal.
Some Poles outside the building on Thursday said they feared rising anti-Polish sentiments among the Belarussian people.
"The authorities of Belarus are provoking the conflict by using force and politicise the organisation themselves," Leon Podlach, 37, told the Associated Press.
"I am afraid of anti-Polish sentiments in the republic."