Serbians voted for a second day on Sunday, on a new constitution that reasserts the nation's claim on Kosovo, the breakaway province whose future status is under negotiation at UN-brokered talks.

A relatively low turnout marked the first day of voting in Serbia.

Referendum authorities say nearly 18 percent of voters had cast ballots by late Saturday afternoon, but no predictions were made about the possible overall turnout.

Turnout is crucial because a majority of Serbia's 6.6 million registered voters must cast a "yes" vote to adopt the constitution.

One voter commented on why the turnout appeared to be relatively low.

"Some people are sick. Some are not very happy with the proposition. Life is hard in Serbia, many have lost hope that things will improve."

However, some of the voters voiced optimism regarding the referendum results.

"I think that everything is going to be good. I expect success for the referendum. I hope for it."

Kosovo Albanians have rejected the Serbian government's offer of broad autonomy, and are seeking independence through negotiations.