Poland has called on the European Union to urge Belarus to respect the rights of the Polish minority there.
The Union of Poles has been targeted by Belarus police
Polish Foreign Minister Adam Rotfeld says a clampdown is underway aimed at destroying "all elements of political pluralism and independence".
The diplomatic move follows a police raid on the headquarters of the Polish community in Belarus earlier this week.
Belarus President Alexander Lukashenko has accused the Polish community of plotting to overthrow him.
"The EU should take decisive and co-ordinated steps and urge the Belarusian regime to respect human and national minority rights, international law and bilateral treaties," Ms Rotfeld said in a letter to Britain's Foreign Secretary Jack Straw.
The UK currently holds the EU presidency.
Copies of the letter were also sent to EU foreign policy chief Javier Solana and EU external affairs commissioner Benita Ferrero-Waldner.
Russia, too, should do more to ensure Belarus respects the rights of its minorities, Poland's Deputy Foreign Minister, Jan Truszczynski, said.
France has already expressed solidarity with the Poles and said it intends to urge the Union to take a firm stand on the issue of human rights in Belarus.
Reporters Without Borders has condemned the arrest of several journalists from the Polish minority.
Mr Lukashenko accuses Poland of seeking to stir up protests against his government to oust him.
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.
They reinstated the association's former leadership which is believed to support Mr Lukashenko's Soviet-style regime.
About 400,000 ethnic Poles live in Belarus, in areas that were part of Poland until World War II.