Campaigning in the Serbian presidential election has ended, with candidates calling on voters for a massive turnout on Sunday.

Two years after the fall from power of Slobodan Milosevic - now on trial for war crimes in The Hague - this election pits supporters of far-reaching economic reform against nationalists and socialists.

Labus wants to carry on with current economic reforms

The poll is expected to be a close race between Yugoslav President Vojislav Kostunica and reformist Deputy Prime Minister Miroljub Labus.

The latest opinion polls have shown Mr Labus neck and neck with Mr Kostunica.

If no clear winner emerges, the two front-runners from a field of 11 candidates will face each other in a run-off in two weeks' time.

It is important to be active in Serbia in order to preserve the federation, but especially to preserve a law-abiding state

Vojislav Kostunica

Supporters of Mr Labus gathered for a final pre-election rally in central Belgrade on Thursday, while Mr Kostunica made an appearance in the southern town of Krusevac.

The third main candidate, the ultra-nationalist Vojislav Seselj - who is supported by the former Yugoslav president Slobodan Milosevic - was barred by United Nations police from entering Kosovo for an election rally.

The authorities were concerned that his appearance could provoke tension in the province, where some ethnic Albanians are seeking to achieve complete independence from Serbia.

Two surveys published on Thursday suggested that none of the candidates will win the first round of the election outright and that most likely a second-round run-off will be held next month, which is expected to favour Mr Kostunica.

Most of the other candidates' voters are expected to switch allegiance to Mr Kostunica if no candidate wins the first round, says the BBC's Nick Thorpe.

'Mafia state'

Mr Kostunica has said he decided to run for the Serbian presidency to preserve the Yugoslav federation and establish the rule of law two years after Mr Milosevic was ousted.

Kostunica is a fierce critic of the Serbian Government

"It is important to be active in Serbia in order to preserve the federation, but especially to preserve a law-abiding state," he told the French news agency AFP.

"Otherwise, it may look tomorrow very much like a mafia state, like some other post-communist states."

Mr Kostunica was hailed as a hero when he won the 2000 federal elections and toppled Milosevic as Yugoslav president, amid a popular uprising.

With the Yugoslav Federation set to be replaced on the map of Europe by a looser union, known simply as Serbia and Montenegro, Mr Kostunica has decided that contesting the post of Serbian president is his best chance of holding on to political influence.