Al-Hariri's coffin, draped in a Lebanese flag, was placed in an ambulance as a military helicopter hovered overhead on Wednesday.
His sons, relatives, aides and supporters walked behind the ambulance while his wife and other female relatives looked on and waved from a balcony.
A huge crowd chanting anti-Syrian slogans crowded the neighbourhood outside his home, blanketed by a sea of Lebanese flags, banners and portraits of the five-time former prime minister.
At least 150,000 Lebanese turned to al-Hariri's funeral
In tears, his sons and relatives bore his coffin which at one point opened as it became caught in the crush.
Some mourners fainted amid chaotic scenes as the crowd surged around the coffin before al-Hariri was laid to rest in the grounds of the mosque a few hundred meters from the seafront.
Aljazeera learnt that Bahaa al-Din al-Hariri, al-Hariri's son, was transferred to hospital suffering fatigue and exhaustion at the funeral procession.
Ghassan bin Jiddo, director of Aljazeera's Lebanon office, said that although al-Hariri's family started preparations for his funeral on Tuesday, some government officials asked the family to allow a national funeral so officials could participate.
Mourners laid flowers outside
The family declined.
Bin Jiddo said opposition figures, including al-Hariri's son, held the Lebanese government responsible for his assassination in a car bomb on Monday.
Aljazeera learned that the head of the Lebanese Parliament, Nabih Barri, and Hizb Allah secretary-general Hasan Nasr Allah may participate in the funeral.
Nasr Allah for the first time said he had been meeting al-Hariri at least once a week during the past months.
Other regional and foreign officials, including US assistant secretary of state for Middle East affairs, William Burns, were expected to join the service.
French President Jacques Chirac was also expected to arrive in Beirut for the funeral.
Thousands of chanting, flag-waving mourners gathered on Wednesday in a prelude to the funeral procession for the man credited with rebuilding post-civil war Lebanon and seen as quietly opposing Syrian influence in his country's affairs.
Plots have been prepared for
al-Hariri and his slain bodyguards
A huge security operation was organised for the funeral, which was to start at his palatial Quraitim compound in Beirut and wind for about 3km through the capital to his burial at the towering Muhammad al-Amin mosque, which he helped build.
The coffins of five of his bodyguards, also killed in Monday's bomb blast, were also to be carried in the procession.
Prelude to funeral
Early on Wednesday, al-Hariri's casket was moved to his home in a convoy of ambulances from the American University hospital, where his body was initially taken after the blast.
More than 50 grieving supporters, bodyguards and relatives, including one of al-Hariri's sons, Saad al-Din, carried his casket into his residence, before a Sunni Muslim cleric began readings from the Quran.
More than a hundred chanting mourners crowded into a room where his coffin was placed, some dancing in a traditional Lebanese display of grief as they held al-Hariri's coffin above their heads.