Serbian security forces on the Kosovo border were ordered to a state of "full combat readiness" on Monday, according to Sky News.

Bratislav Gasic, Serbia's interior minister, said in a statement that he was acting on instructions from President Aleksandar Vucic so that "all measures be taken to protect the Serbian people in Kosovo."

According to Sky, Kosovo has not responded.

The move followed weeks of increasing tension between the two wartime Balkan adversaries, with ethnic Serbs claiming harassment from the ethnic Albanian majority in Kosovo.  

In 1999, the war in Kosovo ended, with NATO intervention, and Kosovo declared independence in 2008. Serbia has not recognized Kosovo's sovereignty and has warned repeatedly that it will protect local Serbs from attack "with all means."

Ethnic Serb mayors, judges, and police officers in the north region of Kosovo resigned en masse last month to protest the decision by Kosovo's government to replace Serbian-issued vehicle license plates with ones issued by capital Pristina, according to Sky.

Earlier this month, thousands of Serbs in Kosovo called for the Albanian majority government to withdraw police from the north and local Serbs have put up nine roadblocks in the northern region since Dec. 10.

According to ABC News, NATO-led peacekeepers on Monday said they are investigating a shooting in one of the northern towns where tensions have been running high.

The incident reportedly occurred Sunday night in Zubin Potok, one of the towns that erected a road barricade.

Known as KFOR, the peacekeepers said the shooting happened near one of their patrols and involved unknown people. In a statement, KFOR said no one was injured and "we are working to establish all the facts."  

According to Sky, the European Union has been attempting to mediate, and Serbia, armed with Russian support, has agreed to talks between the two sides.

• Serbs Put up New Roadblocks as Tensions Soar in Kosovo
• NATO Probing Shooting Incident in Tense Kosovo North