Kosovo Prime Minister Albin Kurti has called on Western countries to impose sanctions on Serbia in response to Sunday's attack that killed a Kosovo police officer and three Serb militants.

Kurti told parliament: "Serbia must be punished for that."

If sanctions are not imposed, it will "bring it back" because "the military arsenal of Serb professionals who attacked in Banjska was made up of weapons from Serbia," he said, referring to the large arsenal that Kosovo authorities say they seized in the northern Kosovo town during an operation against the group after a Kosovo Albanian policeman was killed in an ambush.

A list published by Kurti said the arsenal included an armoured vehicle, grenades, Kalashnikov assault rifles and rocket-propelled grenades worth millions of euros. Belgrade has denied Pristina's accusations from the outset.

The policeman was killed on Sunday just a few kilometres from the border with Serbia during a patrol, followed by hours of gunfire between Kosovo police and the heavily armed group of 30 armed men holed up in a monastery.

Three were killed and 3 arrested, while the fate of the rest remains unknown, and Kosovo maintains that many of them are in Serbia and are being treated in a hospital in the south of the country.

Kosovo, which is mostly Albanian, seceded from Serbia in 1999 after battles involving NATO and declared independence in 2008.

The Serb minority is concentrated in northern Kosovo.