This comes after Serbia deployed armored vehicles at a border crossing and ethnic Serbs in Kosovo protested a decision by Kosovo's government concerning license plates.

Video footage shows NATO armored vehicles moving close to barricades made of trucks and other vehicles on the Kosovo-Serbia frontier, as Serbian government jets fly overheard.

Serbs from Kosovo's north have blocked two main roads since the number-plate ban went into force on Monday last week, exacerbating tensions between the two countries and prompting calls for calm from NATO and the European Union.