NATO chief Jens Stoltenberg said on Wednesday that the alliance had increased its presence in northern Kosovo, ahead of talks between Belgrade and Pristina scheduled for Thursday.

EU mediators are hoping to de-escalate tensions in the western Balkans following unrest in northern Kosovo.

On Wednesday, Stoltenberg met with Kosovo's Prime Minister Albin Kurti and Serbia's President Aleksandar Vucic in Brussels.

What did Stoltenberg talk about with Vucic?

At a joint press conference with Vucic, Jens Stoltenberg said that NATO was prepared to deploy additional forces and had already strengthened its presence in Kosovo.

"We have now a significant mission, a military presence in Kosovo close to 4,000 troops," Jens Stoltenberg told a news conference after talks with Vucic. 

Stoltenberg said that the NATO peacekeeping force in Kosovo (KFOR) was ready to intervene "if stability is jeopardized." He added that the force "will take any measure that is necessary to ensure a safe and secure environment and freedom of movement for all the people of Kosovo."

Vucic said that he informed Stoltenberg of what he called "incidents" and "attacks" on Kosovo's Serbian population, the N1 broadcaster reported.

Vucic denied that Belgrade was planning "any sort of invasion," stressing that Serbia's military and police had not crossed the administrative line that divides territory controlled by Belgrade and Pristina. He added that Belgrade will continue to respect KFOR's mandate in accordance with international norms.

However, Vucic said that talks with Pristina will be difficult because the two sides "disagree on almost everything."

Asked about Western concerns that Russia could open a military base in Serbia, Vucic said that Serbia "doesn't need anyone's military bases" and reiterated Belgrade's military non-alignment, N1 reported.

What did Kurti say in Brussels?

Kurti said that Kosovo's government is dedicated to Euro-Atlantic values and thanked NATO for its presence and role in the western Balkans over the past 23 years, Kosovo news website Kossev reported.

Kosovo's prime minister accused Belgrade of running "illegal structures" which turned into "illegal gangs" that put up blockades in the latest unrest. He stressed that Pristina will show "zero tolerance towards crime and corruption."

Kurti said that police had arrested "dozens of criminals." He added that Kosovo's police doesn't treat criminals differently according to their ethnic origin.

The Kosovo leader also argued that Belgrade had agreed to stop producing license plates for use by Kosovo Serbs — a sore point in the latest standoff between Belgrade and Pristina.

Why are there tensions between Belgrade and Pristina?

Kosovo, which has a majority Albanian population, declared its independence from Serbia in 2008. Belgrade still considers Kosovo to be a province of Serbia and maintains a degree of control over Serb-majority areas of northern Kosovo.

The latest round of tensions between Serbia and Kosovo began last month as Pristina declared that Serbian license plates would no longer be valid in Kosovo territory and that people entering Kosovo with Serbian IDs would need to obtain an additional Kosovar document. Kurti then postponed the implementation of this measure to the start of September following Western pressure.

Members of Kosovo's Serb minority put up roadblocks, sounded air raid sirens and fired guns into the air in protest against the planned measure.

Pristina accused Serbia of instigating the riots. In turn, Serbian officials accused Kosovo of planning a "pogrom" of its Serb minority.

Earlier this month, Kosovo authorities closed two border crossings into Serbia.

sdi/dj (AP, Reuters)