Police in Kosovo stopped Serbian ballots from entering the country in the run-up to a referendum that allows for the participation of Kosovo's ethnic Serb minority, police said on Saturday.

A Serbian election official and two trucks carrying the ballot papers were briefly held at the Merdare border crossing on Friday. Police said they confiscated the trucks and sent six people back to Serbia.

The about 100,000 ethnic Serbs who live in Kosovo are entitled to vote in the Serbian referendum, but Kosovo's government insists that they vote as citizens in a foreign territory would, rather than at formal polling stations.

In an extraordinary session on Saturday, 76 of 120 deputies voted in favor of a declaration banning Serbia from opening polling spots in Kosovo.

Why did Kosovo stop the ballots from being delivered?

Serbia is holding a referendum on Sunday on changes to the judiciary that would bring it closer to EU norms.

Belgrade has said ethnic Serbs in Kosovo may vote, but Kosovar authorities rejected the previous practice of setting up polling stations in parts of the country with high ethnic Serb populations.

On Friday, a statement from the authorities said Kosovar laws "do not recognize the right of one state to hold a referendum in the sovereign territory of another state,'' adding that "the practices applied so far since 2012 have been unconstitutional.''

They instead propose that the ethnic Serbs send in their ballots via mail or go to the liaison office in the capital, Pristina.

What relationship do Serbia and Kosovo have?

Serbia does not recognize Kosovo's independence, which it declared in 2008, after a violent conflict that left some 13,000 dead and only ended when NATO bombed Serbia in 1999.

Although general interest in the referendum is low, promising the possibility of only minor changes, the dispute over the access of polling officials to ethnic Serb-dominated parts of Kosovo is likely to further stoke the contentious relationship between the countries.

The EU has previously told both Belgrade and Pristina that they need to resolve their differences in order for their bids to join the bloc to move forward but there has been little progress.

ab/sms (dpa, AP)