The prosecutor's office in the southwestern Serbian city of Kraljevo on June 16 ordered an investigation of three Kosovo Police officers detained this week in a border area in disputed circumstances.
The officers are being investigated on charges of unauthorized production, possession, carrying, and trafficking of weapons and explosive substances, the prosecutor's office in Kraljevo said in a statement.
The judge overseeing the preliminary proceedings also ordered the continued detention of the three officers, the statement said.
The Kosovar Foreign Ministry has been informed that the three police officers were ordered detained for 30 days and expressed concerns about how they have been treated.
It has been informed that the officers have been kept in inhumane conditions and deprived of food and adequate medical treatment, Deputy Foreign Minister Kreshnik Ahmeti told RFE/RL.
'What we learned today is serious and very disturbing because of the way they were treated during detention," Ahmeti said, adding that the ministry had asked the Red Cross and the Committee for the Prevention of Torture to look into the treatment of the three officers.
Kosovo says that the three men went missing on June 14 during a patrol aimed at preventing smuggling. Interior Minister Xhelal Svecla accused Serbia of "entering the territory of Kosovo and kidnapping" the three policemen.
Belgrade says the officers were arrested "deep inside" Serbian territory.
KFOR, the NATO-led peacekeeping mission in Kosovo, said in a statement that it remains unclear where the police officers were at the time of their arrest.
The U.S. envoy for the Western Balkans, Gabriel Escobar, called on Serbia to release the three officers, saying they 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," Escobar told reporters in an online briefing.
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 British Foreign Office on June 16 also called for their release and urged Kosovo and Serbia to "exercise maximum restraint, avoid unilateral measures and take immediate action to reduce tensions."
European Union foreign policy chief Josep Borrell earlier on June 16 invited Serbian President Aleksandar Vucic and Kosovar Prime Minister Albin Kurti to Brussels for talks next week on defusing rising tensions.
A spokesman for Borrell said that Vucic and Kurti had been invited to Brussels and that more details were to be made public "at a later stage."
Kurti has said the detention of the officers was an act of aggression by Serbia. Vucic denied the accusations and accused Kurti of inciting conflict.
The mounting tensions prompted Borrell to say the bloc's negotiators were "again in crisis-management mode."
The arrest of the police officers came after weeks of tensions following clashes between ethnic Serbs and KFOR in northern Kosovo that left 30 peacekeepers injured last month.
Meanwhile, at the Merdare border crossing about 60 trucks were waiting on the Serbian side to enter Kosovo, RFE/RL correspondents reported on June 16, after the Kosovar government announced the previous day that it was tightening border controls with Serbia "for security reasons."