Serbian Public Prosecutor’s Office orders continued detention of policemen arrested this week in disputed circumstances.

Kosovo said the three officers were arrested on Wednesday inside its territory by Serbian forces who had crossed the border. Belgrade has said they were arrested inside Serbia by police.

The Public Prosecutor’s Office in Serbia’s southwestern city of Kraljevo said it had charged the three policemen with unauthorised production, possession, carrying and trafficking of weapons and explosive substances.

“The judge for the preliminary proceedings of the Higher Court in Kraljevo ordered the detention of all suspects,” the prosecutor’s office said in a statement.

A US envoy called on Serbia to release the trio, saying the officers did not intentionally cross the border and the “likely scenarios” were that they were abducted from inside Kosovo or “inadvertently crossed the boundary”.

The three “had no intention to be in Serbia and should be released”, US Deputy Assistant Secretary of State Gabriel Escobar told an online briefing for reporters.

This “escalation on top of a previous escalation” is “really creating some very difficult conditions for the region, not just for Serbia and Kosovo”, Escobar said.

The detentions were the latest in a series of incidents that have led to unrest in the area and raised concerns about renewed violence between Serbia and Kosovo.

Kosovo’s Prime Minister Albin Kurti has demanded the release of the three, saying their arrests were an act of aggression by Serbia. In response to the arrests, Kosovo has banned all vehicles with Serbian licence plates from entering its territory.

Serbian President Aleksandar Vucic denied the accusations and accused Kurti of inciting conflict.

The United States and the UK urged Kosovo and Serbia to reduce tensions, and called for the immediate release of the Kosovo policemen, while EU’s foreign policy chief Josep Borell has called crisis talks with Kurti and Vucic for next week.

Albanian-majority Kosovo declared independence from Serbia with the backing of the West following a 1998-99 war. Serbia still considers Kosovo part of its territory.