A surprising kingmaker has emerged in notorious ex-warlord Prince Johnson, who holds nearly 200 000 of the votes thus far counted, and official results put Sirleaf ahead with 44.5% to Tubman's 26.5%.

Polls chief James Fromayan will be announcing new results on Friday afternoon.

However, observers believe the trends are likely to hold, and this year's Nobel Peace prize-winner and her rival will probably have to court the ex-warlord in an eventual second round of voting, set down for November 8.

"He is a key player, he holds the balls right now to say whether [Sirleaf's] Unity Party gets in the chair, or whether the CDC [Tubman's Congress for Democratic Change] will be able to unseat the Unity Party," political analyst Alvin J Wright told AFP on Friday.

Johnson, who ordered his soldiers to hack off the ears of dictator Samuel Doe while sipping a Budweiser in 1990 – in a video still available on YouTube – says he has yet to decide who he will back in an eventual second round.

"I will decide whom to support, I don't want to jump the gun, that's my trump card," Johnson, an elected senator, told AFP in an interview.

The election, seen as key to cementing the country's fragile eight-year peace after two back-to-back civil wars, has been lauded as peaceful by the UN and African observers.

"Each area has its own peculiar situation to cope with in terms of delivering the results so we are pleased with what is coming in – tomorrow there will be a lot more than what we are giving today," Fromayan said on Thursday.

Tubman, who is hoping to win with the powerful mix of his Harvard education and football star running mate George Weah, has complained about ballot stuffing, but Fromayan of the NEC said no official complaint had been filed.

Observers from the Carter Centre reported complaints about the misuse of state resources for campaigning purposes and urged parties not to make any statements concerning the results until the process was complete.

Voter turnout so far among a possible 1.8 million voters is put at 70.2%. The electoral commission has until October 26 to announce the final results.

Sirleaf was jointly awarded the Nobel Peace prize just days before Tuesday's vote, for her work in rebuilding the country and promoting women's rights after the civil war in which some 250 000 people were killed.

Her rival Tubman criticised the timing of the award and said Sirleaf does not deserve it as she had failed to reconcile a nation anguished after the war fought by numerous rebel factions, some using drugged-up child soldiers and maiming, raping and terrorising citizens.

Sirleaf has been criticised for dragging her feet in implementing recommendations by a Truth and Reconciliation Commission which names her on a list of people who should be barred from public office for backing ex-warlord-turned-president Charles Taylor.

Taylor is currently awaiting judgement by the International Criminal Court for war crimes committed in neighbouring Sierra Leone, but he has never been prosecuted for atrocities committed in his own country.

The 8 000-strong UN mission in Liberia is providing security back-up as the country prepares for the announcement of the results, often the most potentially dangerous moment in African elections.