"We are sending a clear and strong message to the Belarusian authorities and also to the Polish authorities, a message of support, a message of concern", he added, calling on Minsk to fall in with human rights norms under its Organisation for Security and Cooperation in Europe (OSCE) obligations.

The statement comes after Belarusian police forced its way into the headquarters of the Polish Union of Belarus (ZPB) in Hrodna last night, temporarily arresting several Polish and Belarusian journalists as well as ZPB activists, with three people facing 10-15 days in gaol.

The move follows Minsk's attempts to place pro-government figures at the head of ZPB, the largest and strongest NGO in the country, and the expulsion of three Polish diplomats earlier this month.

Poland calls for EU action

Wednesday's raid provoked a strong reaction from Poland, with Warsaw recalling its ambassador to Minsk, Tadeusz Pawlak.

Foreign minister Adam Rotfeld told press that "Polish-Belarusian relations have arrived at a very serious crisis".

He plans to send three letters to EU foreign policy chief Javier Solana, external relations commissioner Benita Ferrero-Waldner and UK Presidency chief Jack Straw on Friday.

The letters are likely to call for EU sanctions against Minsk in the name of protecting the Polish ethnic minority, but the precise nature of the request is under wraps for now.

Polish lower house speaker and leading presidential candidate Wlodzimierz Cimosiewicz also called for the UN, EU member states and Russia to condemn the latest "scandal".

The Polish parliament is currently pushing through a resolution calling on the EU to extend a travel ban on Belarusian politicians, bring in economic sanctions, boost support for NGOs and block Belarusian athletes from competing in international sports events.

EU reluctant to intervene

The European Commission said it will keep on monitoring the situation in Belarus for now, but that any action is unlikely before the next informal meeting of EU foreign ministers in September.

Member states have already kick-started a process that could see Minsk expelled from the general system of preferences on trade by late 2006, which could bring in steep tariffs on trade just in time for Belarus' presidential elections.

But Brussels is keen to play down the Warsaw-Minsk row as a "bilateral matter" for now.

One western European diplomat told EUobserver that "most of the institutional moves have already been made" when it comes to the Belarus problem, with most member states keen to maintain some dialogue with Minsk via their embassies or international fora such as the OSCE.

He added that Poland and Belarus have a long history of bellicose statements and that ZPB is being targeted because Warsaw is a vocal supporter of regime-change in the region.