President Saakashvili is a close ally of the United States

With more than 80% of votes counted he has won nearly 52%, Georgian television reports. Any more than 50% would mean he would avoid a second-round vote.

The opposition has already alleged the vote was rigged and mounted protests in the capital, Tbilisi.

But international monitors said the vote was essentially democratic.

We will defend our vote by legal means Levan Gachechiladze Protesters' icy reception Bruising battle for Georgia

"According to these results, there is a fairly high probability that everything will be finished in the first round," central electoral commission chairman Levan Tarkhnishvili said.

Mr Saakashvili's main rival, wine producer Levan Gachechiladze, was in second place with about 25% of the vote after Saturday's poll, officials declared.

Results disputed

Mr Saakashvili, a US-educated lawyer, swept to power after street protests in 2003, dubbed the "Rose Revolution".

He called the snap election in an attempt to prove his democratic credentials after huge opposition protests were suppressed last November.

Thousands of opposition protesters disputed the result

"The elections proceeded calmly, in an organised way... the important thing is that we won," he told reporters on Monday.

The coalition of Georgian opposition parties has issued what it says is evidence of fraud, including fake ballot papers and illegally altered election reports.

Their candidate Levan Gachechiladze told the BBC there should now be a second round of voting.

On Sunday, he told thousands of supporters in Tbilisi that results had been "falsified".

Both Mr Saakashvili and Mr Gachechiladze celebrated midnight Mass on Sunday evening, standing near each other at an Orthodox Christmas service in a Tbilisi church.

International thumbs-up

The president was given a significant boost when international observer missions dismissed allegations of fraud.

US Congressman Alcee Hastings of the Organisation for Security and Co-operation in Europe (OSCE), said: "I perceive this election as a valid expression of the choice of the Georgian people."

He said there had been some shortcomings - notably that Mr Saakashvili's campaign had overlapped with state activities, and this "contributed to an inequitable campaign environment".

But he praised the "calm and peaceful atmosphere" during the election, in which he said "democracy took a triumphant step".

Matyas Eorsi, the head of a monitoring group from the Council of Europe, also endorsed the election.

The European Union presidency congratulated the Georgian people on their "peaceful" election.

Georgians in Tbilisi talk about their voting intentions In pictures

But the EU statement also urged Georgia to "do more to reinforce the independence of state institutions in a political campaign environment".

Georgia should also strengthen media freedom and pluralism and the independence of the judiciary, the EU said.

Russia called the election observers' verdict "hasty" and "superficial".

Georgians were also asked to vote on whether they should have a parliamentary election in the coming months, and whether the country should join Nato. The results of those ballots are not yet clear.

Mr Saakashvili's term as president has seen Georgia strengthen its ties with Nato and the European Union.