A Serbian court has ordered the continued detention and investigation of three Kosovo policemen arrested this week in a border area in disputed circumstances. Kosovo says the three were arrested inside its territory by Serbian officers who had crossed the border. Officials in Belgrade say they were detained inside Serbia. 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. Kosovo's Justice Minister Albulena Haxhiu said the policemen must be released as soon as possible. "The scenario to further deepening of tensions is continuing from an aggressive Serbia through the autocratic president Vucic," Haxhiu said in a statement. A US envoy called on Serbia to release the three, 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 reporters. The detentions were the latest in a series of incidents that have led to unrest in the area and raised concern of renewed violence between Serbia and Kosovo. 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 Kosovo government has called the arrests an act of aggression by Serbia and in retaliation has banned all trucks with Serbian licence plates and Serbian goods from entering its territory. Serbian President Aleksandar Vucic denied the accusations and accused Kosovo's Prime Minister Albin Kurti of inciting conflict. The United States and the United Kingdom have 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 United States following a 1998-99 war. Serbia still considers Kosovo part of its territory. Australian Associated Press