Voters in Montenegro - the smaller of the two republics that make up Yugoslavia - have failed to elect a new president because of low voter turn-out, according to preliminary results.

Independent election monitors say under 46% of the electorate took part in Sunday's vote - the law requires at least 50% to make a ballot valid.

Filip Vujanovic, the parliamentary speaker and former prime minister, was in the lead with some 86% of votes, in a election boycotted by the opposition.

The poll was also overshadowed by a sex scandal which erupted earlier this month when police arrested Montenegrin Deputy State Attorney Zoran Piperovic, in connection with human trafficking and forced prostitution.

Local media coverage has focused on the allegations of sexual slavery by a Moldovan woman, who has implicated a number of senior officials.

Mr Vujanovic, who backs full independence for Montenegro, was being challenged by 10 other candidates.

The main opposition party - which prefers continued ties with Serbia, Montenegro's senior partner in the Yugoslav federation - had urged its supporters to stay away.

In neighbouring Serbia - Montenegro's partner in the Yugoslav federation - low turnout also invalidated two attempts in the past three months to elect a president.

Remaining confident

Mr Vujanovic was upbeat as he cast his vote.

Vujanovic: Overwhelming support

"The elections are going to be successful, and I will be the absolute winner," he said.

Mr Vujanovic's close ally Milo Djukanovic, who resigned the presidency last month to become prime minister, also expressed confidence the elections would succeed.

"Montenegro must have all state institutions fully functioning... in order to carry on with social and economic reforms," he said.

But many young Montenegrins were not swayed by these arguments.

"I just don't care any more," said 28-year-old Predrag Starcevic, who is unemployed.

Election boycott

Mr Djukanovic's governing Democratic Party of Socialists achieved a landslide victory in parliamentary elections in October, campaigning on a platform of independence from Serbia.

The heavily defeated opposition, the Socialist People's Party (SNP), decided not to field a candidate for the presidential poll, focusing its efforts instead on invalidating the race through a boycott.

The SNP has accused the government of pressurising workers at state-run institutions to vote for Mr Vujanovic or risk losing their jobs.

Sunday's poll was monitored by the Organisation for Security and Co-operation in Europe and the Council of Europe, as well as local observers.

A repeat vote will be held next month once the poll has been officially declared void.