They were released in the southern Serbian town of Prokuplje to members of the European Union’s police and justice mission operating in Kosovo since the majority-Albanian territory declared independence in 2008.

Serbia does not recognize the secession, and tensions are rising over a plan by Belgrade to hold local elections in some Serb-populated areas of Kosovo when Serbia holds parliamentary and local polls on May 6.

“The two Kosovo police officers are inside Kosovo now,” said Nicholas Hawton, spokesman for the EU mission known as EULEX. “They came from Prokuplje in an EULEX car,” he said.

The arrest of the two officers on Saturday was announced by Serbian Interior Minister Ivica Dacic, whose Socialist Party of Serbia - once led by late Serb strongman Slobodan Milosevic - is vying for a place in Serbia’s next ruling coalition.

He said they were spies and were possibly preparing a “terrorist act.” The interior ministry released photographs of the two men handcuffed and face down in a wooded area with masked members of the Serbian gendarmerie standing over them.

The move drew a furious response from Kosovo, which said the men had been “abducted” from Kosovo-controlled territory and called on the EU and the United States to intervene.

Asked about their release, a Serbian interior ministry official told Reuters: “We have nothing to say. If they have been released that means that the justice ministry and its prosecutor decided so in line with the law.”

The EU has urged Belgrade not to hold its local elections inside Kosovo, and Pristina has threatened to prevent voting.

Belgrade lost control over Kosovo in 1999 when NATO bombed Serbia for 78 days to halt the killing and expulsion of ethnic Albanian civilians by Serb forces fighting a two-year counter-insurgency war.

Kosovo has been recognized by 89 countries, including the United States and 22 of the EU’s 27 member states.