Serbia held a referendum Sunday on constitutional amendments that the populist government says is needed for the Balkan country to advance in a bid to join the European Union.

The ballot focuses on the changes in the election of judges and prosecutors that authorities say are aimed at boosting their independence in the country where the judiciary is widely seen as corrupt and politically controlled.

The referendum has been hailed by the United States, the European Union and some Western countries as a step in the right direction. But critics at home say the changes are insufficient.

Some opposition parties and independent experts also have argued that the referendum was organized in a generally nondemocratic atmosphere, too hastily and too soon before an election that is due in early April.

President Aleksandar Vucic's government has faced accusations of curbing democratic freedoms, which they have denied. Vucic and other officials on Sunday urged voters to support the amendments and help the country move forward.

About 6.5 million Serbian citizens were eligible to vote in the referendum. A simple majority of those who turn out decide on the outcome. Official results were expected on Monday.

The government has urged the Serb minority in Kosovo – a former Serbian province that declared independence in 2008 – to come to nearby towns in Serbia to cast ballots after Kosovo authorities refused to allow for the opening of polling stations there.

Dozens of Kosovo Serbs on Sunday held a protest in the Serb-dominated northern part of Kosovo. No incidents were reported.

Serbia doesn't recognize the independence of Kosovo, which has been backed by the U.S. and most EU countries. Serbia and Kosovo must normalize relations to be able to advance toward EU membership.