Early returns, about three per cent, compiled by the country's Independent Radio Network from results obtained at counting centres showed the APC, the one-time sole ruling party in the country, ahead of the SLPP.
"I hope the people of Sierra Leon can have this election without violence. All that is needed is one act of violence to spark another civil war."
Tom Dougherty, Atlanta, USA
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Complete preliminary results are expected by the end of the week.
The trend so far shows that both parties maintained dominance in their traditional strongholds, APC in the north and SLPP in the south.
However, the SLPP has found itself being challenged in the south by the People's Movement for Democratic Change, its offshoot party.
If none of the presidential hopefuls garners at least 55 per cent of the ballots cast, a second round of voting will take place.
Ahmad Tejan Kabbah, who has led the country as president for two five-year terms, was not eligible to stand for re-election.
Voting was said to be generally peaceful, although some polling stations opened late and many people had to wait in long lines under the rain to cast their ballots.
However, one voter, Phillip Namara, 38, told Al Jazeera: "They're not allowing me to vote, they're not allowing me to exercise my rights."
After arriving at the centre and being assigned his voter registration card, Namara said he was told to go to another polling station.
At the second centre, they told him they did not have his information and to return to the first station. When he was again told his registration could not be verified, Namara decided not to vote.
Koroma told Al Jazeera the election was a "very good day for Sierra Leone".
He said he was confident of victory even if there was a further run-off vote to decide the presidency.
The APC leader said: "We have also made substantial inroads. We have been welcomed in areas that are not normally our strongholds. I am confident of victory - even if there is a run-off I am going to win."
Armed police were deployed in parts of Freetown after youths tried to disrupt vote counting, but police said the rest of the night passed off peacefully.
|Sierra Leone is the second poorest |
country in the world
Richard Moigbeh, police assistant inspector-general said on Saturday evening that tear gas was fired to disperse youths who wanted to disrupt vote collating in parts of Freetown.
Christiana Thorpe, head of the National Electoral Commission said: "Armed security has now been provided to all polling stations in this area so that counting can continue."
Observers fear tensions might rise among party supporters after election results are announced.
About 2.6 million voters were eligible to pick a new president and representatives, six years after the end of the Sierra Leone's civil war.
In all, seven political parties fielded candidates in a country ranked the second poorest on earth, despite its huge mineral resources including diamonds.
Legislators are elected by a simple majority, and 566 candidates stood for the 112 seats in the single-chamber parliament.
The elections are only the second since the country emerged from one of the most brutal wars in modern history, and the first poll Sierra Leone has organised after 17,500 UN peacekeepers pulled out of the country in December 2005.
A civil war, fuelled by blood diamonds, ravaged Sierra Leone between 1991 and 2001, claiming 120,000 lives while hundreds of thousands of survivors suffered horrors at the hands of fighters.