Serbia's President Aleksandar Vucic talks to the press as he arrives for the EU-Western Balkans summit in Tirana, on Dec 6, 2022. (LUDOVIC MARIN / AFP)

BELGRADE / BRUSSELS – Serbia demands the release of all arrested Serbs from northern Kosovo, but also seeks to defuse tensions there following tensions in the restive region, President Aleksandar Vucic said on Sunday.

After a meeting of the National Security Council, Vucic said Kosovo Serbs must not engage in violence against NATO troops and members of the European Union mission there.

No one, under no circumstances should be involved in attacks... on Eulex and KFOR.

Aleksandar Vucic,

Serbia President 

"No one, under no circumstances should be involved in attacks ... on Eulex and KFOR," he told Reuters in his office in Belgrade.

Vucic declined to elaborate on the steps the National Security Council adopted. Asked whether Belgrade would seek to de-escalate the situation in northern Kosovo, he replied: "Absolutely."

Serb protesters in northern Kosovo blocked main roads on Saturday after the arrest of a former Serb policeman. Kosovo police later came under small-arms fire in several locations and a stun grenade was thrown at a car belonging to the EU mission in Kosovo. There were no injuries.

For a second day on Sunday, trucks and other heavy-duty vehicles blocked several main roads leading to two border crossings with Serbia. Both crossings were closed to traffic.

EULEX, the European Union mission tasked with patrolling northern Kosovo, said a stun grenade was thrown on one of its armored vehicles on Saturday evening, but no one was injured.

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Following the flare-up, EU, the United States, and NATO asked for restraint by both parties and demanded the removal of barricades.

Vucic accused authorities in Pristina and Kosovo's Prime Minister Albin Kurti of stoking tensions by making "countless unilateral moves."

Kosovo declared independence from Serbia in 2008, following the 1998-99 war in which NATO intervened to protect Albanian majority Kosovo

"Whenever one would think we have something solved, another problem emerges," Vucic said.

Serb mayors in northern Kosovo municipalities, along with local judges and some 600 police officers, resigned last month in protest over a Kosovo government move to replace Belgrade-issued car license plates with ones issued by Pristina.

Kosovo later agreed to postpone the decision and Belgrade said it will stop issuing new Serbian car numbers.

Vucic demanded the release of recently arrested Kosovo Serbs "as they are held on trumped-up charges" and the pullout of Kosovo police, in line with an EU-brokered agreement that stipulates consent of Serb mayors in the area for that.

READ MORE: Kosovo Serb leader shot dead in northern town

"Kosovo police has nothing to do in the north... , especially people armed ... up to their teeth," he said. "That causes uneasiness and fear among the Serb population."

On Saturday, Vucic said Belgrade would ask KFOR to let Serbia deploy military and police in Kosovo, but acknowledged there was no chance of permission being granted.

Kosovo declared independence from Serbia in 2008, following the 1998-99 war in which NATO intervened to protect Albanian majority Kosovo.

Belgrade and Pristina are holding talks in Brussels to try to normalize relations and the EU has already presented a plan.

Heavy vehicles parked by local Serbs block the road in the village of Rudare, northern Kosovo on Dec 11, 2022. (VISAR KRYEZIU / AP)

Kosovo and Serbia must de-escalate a tense situation in the region, the European Union's foreign policy chief said on Monday, after Serb protesters in northern Kosovo blocked main roads for a second day on Sunday.

"I know the two parts are willing to de-escalate and I strongly call on the two of them to do it," Josep Borrell, High Representative of the European Union for Foreign Affairs and Security Policy, also Vice-President of the European Commission, said as he arrived at a meeting of EU foreign ministers. "They have to come back to the dialogue, they have to overcome this tendency to fighting in the street."

READ MORE: Kosovo, Serbia reach deal to end dispute over car plates

Borrell said the violence used by both sides in the recent protests was unacceptable.