Updated

An elaborately decorated Serbian nationalist train took off Saturday from Belgrade aiming for northern Kosovo but halted at the border in a stunt that triggered a dramatic escalation of tensions between the former wartime foes.

Kosovo officials had protested earlier that the train was in violation of their country's sovereignty and promised not to let it in.

Serbian Prime Minister Aleksandar Vucic ordered the train stopped at the Serbian town of Raska as it approached the border with Serbia's former province, claiming that Kosovo's ethnic Albanians had tried to mine the railway.

Kosovo police strongly denounced such accusations but said they had had checked the railway and found no explosives.

Kosovo Prime Minister Isa Mustafa said he had contacted the United States and the European Union to express his country's concerns.

"I believe that turning back the train was the appropriate action and its entry into the independent and sovereign Republic of Kosovo would not be allowed," he said at a Saturday evening news conference.

The Russian-made train was painted with Serb flags, religious Christian Orthodox scenes, monasteries and medieval towns and inscribed with "Kosovo is Serbian" in 20 world languages. Hostesses on it wore the colors of the Serbian national flag.

Kosovo declared independence from Serbia in 2008, but Serbia does not recognize the split and has sought to maintain influence in Kosovo's north, where most of the country's Serb minority is located.

At an urgently called news conference in Belgrade on Saturday, Vucic accused the Kosovo government in Pristina of plans to arrest the train's driver and passengers.

"This was an ambition to provoke a conflict, to start a wider conflict in this territory that we consider as ours," Vucic said. "It was my decision to stop the train in Raska to preserve the freedom and lives of our people, to prevent a wider conflict and show that we want peace."

He warned ethnic Albanians in Kosovo not to attack Kosovo's Serb minority "because Serbia will not allow those attacks."

"We sent a train, not a tank," Vucic said.

NATO-led troops are controlling Kosovo's borders following an intervention in 1999 to stop a bloody Serbian crackdown against ethnic Albanian separatists in Kosovo.

Saturday's promotional ride was the first from Belgrade, the Serbian capital, to the northern Kosovo town of Mitrovica since the 1998-99 war. The train later turned back toward Belgrade.

Kosovo President Hashim Thaci said Saturday on his Facebook page that Kosovo respects the freedom of movement of people and goods but a train covered in nationalist banners that violate Kosovo's constitution and laws "is completely unacceptable."

He also noted the train had some passengers and Serb officials who did not have permission to enter Kosovo.

"Anything that is illegal and threatens Kosovo's state sovereignty, must be prevented. This train is the latest provocation and authorities in Kosovo must use all legal means to stop this train immediately," he wrote.

Earlier, as the train left Belgrade, Marko Djuric, who heads Serbian government's office for Kosovo, described the rail link as important for northern Kosovo.

"This is like a mobile exhibition presenting our cultural heritage," he said.

The clash of viewpoints came amid already heightened tensions between Serbia and Kosovo following the recent detention in France of Ramush Haradinaj, a former Kosovo prime minister, on an arrest warrant from Serbia.

Kosovo has called the warrant not legitimate and urged France to ignore it.