Kosovo’s parliament on Saturday passed a resolution banning ethnic Serbs from voting on Kosovan soil in Serbia’s national referendum on constitutional amendments.

Serbia will hold a referendum on Sunday on amendments to the constitution that would change how judges and prosecutors are elected, a move the government says is aimed at securing an independent judiciary, a condition for EU membership.

Kosovo’s independence backers—the United States, the United Kingdom, Germany, France, Italy and the EU mission—urged Prime Minister Albin Kurti to allow Serbs in Kosovo to vote in the referendum.

But in an extraordinary session on Saturday afternoon, 76 out of 120 deputies voted in favor of a declaration banning Serbia from opening polling centers in Kosovo.

Kurti told parliament that establishing polling stations in majority Serb areas of Kosovo would be against the constitution, and that ethnic Serbs could vote by mail or in Belgrade’s government liaison office in Pristina.

“Kosovo is an independent and sovereign state and should be treated as such,” Kurti said.

Serbia, which still considers Kosovo part of its territory, has been organizing elections for its ethnic kin since the Kosovo War ended in 1999.

Serbia refuses to recognize Kosovo’s 2008 declaration of independence but has pledged to normalize relations with its former breakaway province before joining the EU.

The head of Serbian Office for Cooperation with Kosovo said the ban was aimed at “annulling political and civic rights of Serbs [in Kosovo].”

“Kurti and his extremists should not think that in the future they will succeed in banning Serbs in Kosovo from voting, notably in April 3 elections,” Petar Petkovic said in a statement.

Serbia is holding presidential and parliamentary elections on April 3. Early on Saturday, Kosovo police confiscated two trucks of the Serbian election commission transporting ballot papers as they crossed the border at Merdare to head towards Serb-majority areas.

“We call on the Kosovo government to allow Serbs in Kosovo to exercise their right to vote in elections and electoral processes in accordance with this established practice,” Germany, France, Italy, United Kingdom, United States and the EU said in their joint statement Friday.