Kosovo police forces entered the northern village of Banjska on Monday, searching for members of an armed group that opened fire on a police patrol on Sunday.

A group of around 30 individuals killed one officer and barricaded themselves in a local Orthodox monastery on Sunday. In the stand-off that lasted several hours, police forces killed three of the gunmen and injured another two.

Several assailants escaped on foot and remain on the loose. Kosovo says the suspected ethnic Serb gunmen escaped to Serbia and called on Belgrade to extradite them.

"We are demanding from Serbia to hand these men over to Kosovo authorities as soon as possible, to face justice for their terrorist acts," said Kosovo Interior Minister Xhelal Svecla.

Local police forces arrested two of the attackers, as well as four ethnic Serbs who are suspected of supporting them. All six are being investigated for terrorist acts.

Authorities also searched for infiltrators among worshippers in the monastery. 

Two clergymen and a group of pilgrims from Serbia were reportedly staying in the building when the fighting broke out on Sunday. None of them were injured.

Gunmen believed to be ethnic Serbs

It is not yet clear who the attackers are and who is supporting them, but they are widely believed to be ethnic Serbs from northern Kosovo.

Tensions between predominantly Orthodox Serbs and mostly Muslim Albanians in Kosovo have been flaring up over recent months.

According to the Ministry of Interior, police seized arms and explosives that could be used to arm hundreds of people.

On Monday, Kosovar police presented some 20 SUVs and an armored truck they said were used by the gunmen. Three of the vehicles bore the logo of KFOR, NATO's Kosovo peacekeeping mission.

They also displayed a cache of arms, including old Yugoslav army assault rifles, machine guns, sniper rifles, mortars, anti-tank rocket launchers, hand grenades, land mines and drones.

Kosovo's Prime Minister Albin Kurti condemned the incident as a "terrorist attack" and accused Serbia of supporting the "mercenary structure."

Serbia denies involvement

Serbian President Aleksandar Vucic denied any connection to the incident, pointing the finger instead at local Kosovo Serbs, "who no longer want to stand Kurti's terror."

Belgrade has repeatedly accused Kosovo of oppressing Serb communities in the country's north and has demanded more autonomy for them.

While Vucic condemned the attack, he also slammed the West for its "hypocrisy" over Kosovo. "You can kill us all. Serbia will never recognize the independence of Kosovo, that monster creation that you made by bombing Serbia," Vucic said.

US urges 'return to dialogue'

During the Kosovo war in 1999, NATO forces bombed Serbia in a decision that remains controversial. Kosovo declared independence from Serbia in 2008.

Most EU countries recognize Kosovo, but the bloc's efforts to broker peace between the two sides have failed so far.

The United States, which also recognizes Kosovo, condemned the attack. In a statement on Monday, Secretary of State Anthony Blinken said Kosovo and Serbia must, "immediately work in coordination with international partners to de-escalate the situation, ensure security and rule of law, and return to the EU-facilitated dialog."

Russia warns of 'dangerous' situation 

Russia said on Monday it is monitoring the "potentially dangerous" situation in Kosovo. Moscow does not recognize Kosovo's independence and has traditionally supported Serbia in the conflict.

Russia's Foreign Ministry squarely laid blame for the escalation with Kosovo, saying: "There is no doubt that yesterday's bloodshed is a direct and immediate consequence of the course of the so-called 'Prime Minister' Albin Kurti to incite conflict." 

Moscow warned the situation could potentially spiral out of control, pushing "the entire Balkan region to a dangerous precipice,"

"There is a direct threat of the resumption of the ethnic cleansing previously practiced by Kosovo-Albanian radicals,"  it added. 

js,fg/wmr (AP, Reuters)