Kosovo has demanded barriers erected by Serb protesters be removed while Serbia has put its army on high alert.

The new barriers, formed with loaded trucks, were installed in the early hours of Tuesday in the town of Mitrovica. The town is divided between Kosovo Serbs and ethnic Albanians, who represent the majority in Kosovo as a whole.

It is the first time since a crisis in the region erupted in early December that Serbs have blocked streets in one of the main towns. Until now, barricades had been set on roads leading to the Kosovo-Serbia border.

The developments came after President Aleksandar Vucic on Monday ordered Serbia’s army and police to be put on high alert in response to the latest events in the region.

Vucic claimed that Pristina was preparing to “attack” ethnic Serb areas in northern Kosovo and remove by force several of the roadblocks that Serbs started putting up 18 days ago to protest against the arrest of a former Kosovo Serb policeman.

Kosovo’s government has yet to respond to Vucic’s allegations but has previously accused the Serbian leader of attempting to stir up trouble and trigger incidents that could act as a pretext for an armed intervention in the former Serbian province.

Meanwhile, Pristina has asked NATO-led peacekeepers (the Kosovo Force, or KFOR) stationed in the country to remove the barricades set up by ethnic Serbs and hinted that its own forces will do so if KFOR does not take action.

About 4,000 NATO-led peacekeepers have been stationed in Kosovo since the 1999 war that ended with Belgrade losing control over the territory.

Simmering tensions in the Balkans

The latest furore first erupted on December 10, when Serbs erected multiple roadblocks and exchanged fire with police after the arrest of a former Serb policeman for allegedly assaulting serving police officers during a previous protest.

The ethnic Serbs are demanding the release of the arrested officer and have other demands before they will remove the barricades.

It comes after earlier trouble over the issue of car licence plates. Kosovo has for years wanted ethnic Serbs in the north to switch their Serbian car licence plates to ones issued by Pristina, as part of the government’s desire to assert authority over its territory.

Ethnic Serb mayors in northern municipalities, along with local judges and about 600 police officers, resigned last month in protest after Kosovo’s government finally ruled that Serbian-issued licence plates must be replaced with ones issued by Pristina.

Kosovo declared independence from Serbia in 2008 but remains home to a Serb minority in the north backed by Belgrade.

The declaration of independence came 10 years after a war between ethnic Albanian fighters and Serbian forces that killed 13,000 people, mostly ethnic Albanians.

The war ended with a NATO intervention that pushed the Serbian troops out of today’s Kosovo.

Serbia, supported by its allies Russia and China, does not recognise the statehood of its former province but most Western countries do, including the United States.

About 50,000 ethnic Serbs who live there refuse to recognise Pristina’s authority and still consider themselves a part of Serbia.

Belgrade accuses Pristina of trampling on the rights of the minority Serbs.