The anti-Syrian opposition led by al-Hariri captured control of Lebanon's parliament on Monday in the fourth and final round of the country's elections, breaking Syria's long domination of the country.
Interior Minister Hassan Sabei declared anti-Syrian opposition candidates had won all 28 seats in North Lebanon in Sunday's polling.
Asked whether he would seek the premiership, 35-year-old son of the assassinated former prime minister Rafiq al-Hariri said he would consult his allies. He also said he would negotiate with other parliamentary blocs to broaden his alliance.
Extending a hand to his defeated opponents, al-Hariri said: "We have to maintain dialogue with everybody. We will not close the door on anyone."
Saad al-Hariri's anti-Syrian bloc
swept the fourth round of polls
"The north has decided the character of the new parliament and given the absolute majority to the opposition," al-Hariri said.
Al-Hariri and his allies will have 70 seats in the parliament, Aljazeera reported.
Anticipating victory, men, women and children waved flags and danced in the streets of Tripoli, the provincial capital of the north, earlier on Monday.
In Beirut, the national capital, opposition supporters drove through the city, cheering and honking their horns in celebration.
But the election was marred by vote-buying and other shortcomings. The head of the European Union observers, Jose Ignacio Salafranca, said his team of about 100 personnel had "directly witnessed a few attempts at vote-buying" in the three previous rounds of voting.
However, Sabei said: "The Ministry of Interior has accomplished free, honest and neutral elections."
On tour in Middle East, US Secretary of State Condoleezza Rice commended the way the Lebanese had debated during the election. "I think it shows that they can overcome the deep differences that have been in their society."
President Emile Lahoud called on the new parliament on Monday to reform the electoral law to "put an end to vote-buying and give an equal opportunity to all candidates".
The opposition's victory capped four months of political upheaval since the 14 February assassination of Rafiq al-Hariri.
"We have to maintain dialogue with everybody. We will not close the door on anyone"
The killing provoked mass demonstrations against Syria which, coupled with UN and US pressure, forced Syria to withdraw its troops from Lebanon by late April, ending 29 years of military and political dominance.
The opposition blamed Syria and pro-Syrian elements in the Lebanese security services for blowing up al-Hariri's motorcade, killing him and 20 others on a Beirut street.
Syria denies involvement.
The all-too rare Christian-Muslim Lebanese solidarity that emerged after al-Hariri's assassination disintegrated during the campaign. The final round was particularly marred by sectarian appeals as both sides sought to mobilise their supporters.
The new parliament will face the challenge of healing Lebanon's long standing divisions and sectarian tensions.
The parliament also will elect a new speaker and nominate a new prime minister. The outgoing speaker and premier are pro-Syrian.
The new government will have to tackle Lebanon's heavy debt, cooperate with a UN investigation into al-Hariri's assassination, and work out how to approach the deeply divisive UN call for Lebanon to disarm its militias - a reference to the Hizb Allah group, which enjoys strong electoral support and wide respect among Lebanese for its campaign against Israel.