A crisis between Poland and Belarus has deepened with the arrest of two more ethnic Polish leaders by the Minsk authorities.The vice-president of the Association of Poles in Belarus and an adviser to the president have been detained in the western town of Grodno. Police there have refused to comment. The head of the association, who was herself arrested and then released, has thanked several EU countries for their diplomatic support. Between 400,000 and 500,000 ethnic Poles live in Belarus. Minsk has eyed them with increasing suspicion since Warsaw was seen as backing regime change in neighbouring Ukraine last year. Ties between Poland and Belarus chilled further when the deputy speaker of the Polish parliament visited his compatriots in Grodno earlier this week. Minsk criticised the move as direct interference in Belarussian internal affairs. The autocratic president of Belarus, Alexander Lukashenko, fears the Polishminority could be a trojan horse used to oust him in elections due next year. The crackdown has sparked protests outside the Belarussian embassy in Warsaw.