Serbia put its troops on full alert Tuesday after heavily armed Kosovo police entered Serb-dominated northern Kosovo, firing tear gas and arresting about two dozen people.
It was the latest flare-up in long-simmering tensions between Serbia and its former province, which declared independence from Belgrade in 2008 after a bloody 1998-99 war that ended only with NATO intervention. Ninety percent of population in northern Kosovo are Serbs who don't want to be part of independent Kosovo. Action by Kosovo special police there is rare and always triggers Serb anger.
Serbian President Aleksandar Vucic said Kosovo police arrested 23 people, including Serbs, Bosnians and a Russian, after "bursting" into several northern villages and the town Mitrovica with armored vehicles. Vucic said he had seen video of the police firing "live ammunition" over the heads of unarmed Serbs, and said the operation was designed to intimidate minority Serbs in Kosovo, whose population is mostly ethnic Albanians.
Vucic said he has ordered soldiers near the border to be on "combat alert" to protect Serbs if tensions escalate.
"Serbia will try to preserve peace and stability, but will be fully ready to protect our people at the shortest notice," Vucic told parliament.
He later said that the Kosovo policemen were withdrawing.
The U.N. mission in Kosovo said those detained included two of its staff members, one of them Russian. It said both employees were hospitalized for injuries, and called for all parties to help restore calm and security.
Russia, a Serbian ally, called Kosovo's actions a ``provocation'' and demanded the immediate release of the Russian U.N. employee.
Kosovo President Hashim Thaci said earlier that the Russian "was camouflaged under a diplomatic veil to hamper the police operation."
Serbian state TV reported movements of Serb troops stationed near the border. Any Serbian armed incursion into Kosovo would mean a direct clash with NATO-led peacekeepers there.
Kosovo's prime minister, Ramush Haradinaj, confirmed on Twitter that police had carried out "an anti-smuggling and organized crime operation." Thaci called on the ethnic Serb minority to remain calm and support the police.
"Those involved in illegal activities will go behind bars," he wrote on his Facebook page, insisting that the police operation was not targeting people from specific ethnicities.
The spokesman for the NATO peacekeeping mission, Col. Vincenzo Grasso, said the force is monitoring the situation and coordinating with authorities.
"Because of the political sensitivity of the moment, Commander KFOR invites all the parties to deal with the disputes peacefully and responsibly, without any use of force or violence. People should stay calm, they have nothing to fear," the mission said in a statement.
Serbia, and its allies Russia and China, do not recognize Kosovo's 2008 declaration of independence. The United States and more than 100 other countries do. The lingering dispute has stalled both countries' efforts to become members of the European Union.
The two sides had been participating in an EU-facilitated dialogue, but Serbia walked away in November after Kosovo slapped a 100% tax on Bosnian and Serbian imports, saying it will be lifted only when the two countries recognize Kosovo's sovereignty.
