The European Union and the United States expressed their deep concern Sunday after Kosovo banned the use of the Serbian currency and police raided the premises of organizations working with the Serb minority in the north of the country.

In the past week, Kosovo police searched the premises of Serbia-administered institutions and of an ethnic Serb non-governmental organization, confiscating papers and computers believed to hold documentation contrary to the country’s laws.

Some of the documents bore the emblem of the Serbian government in Belgrade, police said, while others referred to illegal parallel structures of government set up by ethnic Serbs but not accepted by Kosovo.

Police closed some of those offices.