The main anti-Syrian opposition alliance, led by Saad al-Hariri, said it was headed for a majority in parliament after claiming a stunning win in Sunday's decisive final round of elections.
The alliance was set to win the 21 seats it needed out of the 28 up for grabs in the voting in the north, according to incomplete results from the count witnessed by his campaign staff.
"According to incomplete results, we are heading to a total victory," leading candidate Boutros Harb told the Future Television channel of al-Hariri.
If confirmed by official results on Monday, the outcome would mark a major coup for the alliance, which had faced an uphill battle after suffering a rout in the third round of elections the previous weekend.
The outcome would give al-Hariri, a 35-year-old businessman turned politician, the opportunity to become prime minister, following in the footsteps of his slain father who held the post five times.
"According to incomplete results, we are heading to a total victory"
Boutros Harb, al-Hariri bloc
But it would fall short of the two-thirds majority required to change the constitution to cut short the term of under-fire pro-Syrian President Emile Lahoud, who has more than two years in office after a controversial Damascus-inspired extension last September.
The four-round elections which kicked off on 29 May were the first since neighbouring Syria ended its three-decades long troop presence in April amid the political turmoil that followed the February assassination of Rafiq al-Hariri.
About 700,000 people in two northern constituencies were eligible to vote on Sunday.
Opposing Saad al-Hariri for seats in the 128-seat house was an unlikely alliance between the Christian general and former exile Michel Aoun and a raft of pro-Syrian figures.
With 21 seats already in the bag from previous rounds, Aoun had threatened to upset al-Hariri list's ambition to take sole control of the long Syrian-dominated legislature.
Al-Hariri's bloc won 44 seats in previous rounds while 35 seats went to the pro-Syrian alliance of Shia factions Amal and Hizb Allah.
Amid a fierce race between the Aoun and al-Hariri lists, turnout on Sunday reached 48%, according to preliminary official estimates, well up on the 40% recorded in the last elections in the northern region in 2000.
In a boost for al-Hariri, participation reached 42% in the main northern city of Tripoli, where turnout had been sufficiently low two hours before the close of polls that he had issued an anxious televised appeal to late voters.
Voter turnout in the North
Lebanon poll reached 48%
"If you don't vote, I won't be able to change anything," he had warned.
In a vitriolic campaign, both sides had repeatedly attacked each other's anti-Syrian credentials, with Aoun accusing al-Hariri and his allies of being belated converts to the cause, while they took aim at his pro-Damascus allies.
Al-Hariri's huge personal fortune also fanned allegations of vote buying. The official ANI news agency reported some minor incidents, including a man arrested in Tripoli after a grenade was found on him, and an exchange of fire between soldiers and a passing car.
In the Syrian border town of Abbudieh, an AFP photographer saw security forces intervene after rival supporters exchanged blows and smashed car windscreens.
A clear-cut outcome was likely to provide a major boost for a country which could ill afford an extended period of uncertainty. The turmoil following February's massive bomb blast which killed Rafiq al-Hariri already dented confidence in an economy burdened with a massive national debt of some $35.5 billion.
The central bank warned last week that it expected gross domestic product to fall this year, with inflation of 4% outstripping growth of 2%.
Security was tight for the election in a region where Syrian troops held sway for years.
As he cast his vote in Tripoli, caretaker Prime Minister Najib Miqati rejected al-Hariri bloc accusations that a continuing Syrian intelligence presence had intimidated voters.
"The voting has been completely free," said Miqati, who was approved as a compromise leader by the opposition despite his links with Damascus.
"There's been no intervention by Syria to influence voters. There are no Syrian agents at work."
European and other foreign observers monitored the conduct of the vote.