Updated

Hundreds of thousands of screaming mourners chanted "Syria out!" as they mobbed the flag-draped coffin of former Prime Minister Rafik Hariri (search) at his burial Wednesday, two days after a huge bomb killed the man credited with rebuilding post-civil war Lebanon.

Suspicions over Syrian involvement in Hariri's assassination charged the atmosphere, with his family and supporters warning officials of the pro-Syrian Lebanese government to stay away.

While a previously unknown Islamic group initially took credit for the blast, many suspect Syria was behind the attack. Syria has an estimated 15,000 troops in Lebanon and has been adamant about keeping them in place, despite demands for withdrawal by the late Hariri and others, including the U.S. and the United Nations. U.N. resolution 1559 was passed in attempt to get Syria to leave Lebanon, to no avail.

Hariri’s death could have global impacts and increase tension in the Middle East. Secretary of State Condoleezza Rice said relations with Syria are worsening and more sanctions against the nation are a possibility.

Syria and Iran, whose nuclear ambitions have Washington on edge, are pledging to work together against a perceived bias against them.

International pressure has mounted to find Hariri's killers, with Washington recalling its ambassador and the U.N. Security Council demanding Lebanon bring those responsible for Hariri's slaying to justice.

In Beirut, more than 200,000 people crowded into a central square around the towering Mohammed al-Amin Mosque (search), which Hariri built. It is also where the billionaire businessman, who was Lebanon's prime minister for 10 of the 14 years following the end of the 1975-90 civil war, was to be buried.

In Syria, government officials were silent as American and U.N. pressure continued to mount.

The assassination "angered the international community, and this requires that we shed the light on this heinous, indescribable act," said French President Jacques Chirac, a friend of Hariri's who flew in to offer condolences.

The U.S. representative at the funeral, Assistant Secretary of State William Burns, called again on Syria to withdraw its troops from Lebanon — a further spike in U.S.-Syrian tensions a day after the U.S. recalled its ambassador from Damascus.

"Mr. Hariri's death should give — in fact it must give — renewed impetus to achieving a free, independent and sovereign Lebanon," Burns said after a meeting with Lebanon's foreign minister.

"And what that means is the complete and immediate withdrawal by Syria of all of its forces in Lebanon," Burns said.

The crowd was the largest seen in Lebanon since the 1997 mass delivered in Beirut by Pope John Paul II, which attracted almost 1 million people.

The funeral, policed by a huge security operation, started at Hariri's palatial Koreitem compound, then wound two miles through the capital's streets before arriving at his eventual burial place.

Grieving relatives, including his three sons, carried Hariri's coffin, draped in a red, white and green Lebanese flag, out of an ambulance and through the heaving crowd.

Many mourners scrambled to touch the casket as it passed by in a sign of respect as thousand of others chanted the Arabic words for "There is no God but Allah."

Hariri's eldest son, Baha, climbed on top of several people's shoulders to yell into a microphone and demand calm from the crowd as his father's coffin arrived at the mosque.

"We don't want his last minutes to be like this — step back away from his body," he pleaded.

Hariri's remains were first brought to his home earlier Wednesday from the American University Hospital (search), where his body was taken following Monday's huge car bombing that killed him and 16 others.

His body was later placed in one of at least six ambulances — one each to carry the coffins of Hariri and five of his bodyguards slain in the huge bomb blast — for transport to the mosque.

With sirens wailing, the ambulances carrying the caskets were followed on foot by Hariri's sons — Baha, Saadeddine and Ayman — who led a sea of mourners waving flags and banners and holding portraits of the billionaire tycoon.

Breaking with Islamic tradition, hundreds of weeping women waving white handkerchiefs joined men in the march. This and the participation of Sunni Muslim clerics, white turban-wearing Druse (search) religious leaders and ordinary Lebanese Shiites and Christians demonstrated Hariri's great popularity and ability to reach across potentially volatile sectarian divides.

Beirut church bells rang loudly as the procession neared, mashing with a cacophony of military band drum beats and mourners chanting slogans and Islamic prayers through megaphones.

Those who could not come to Beirut had their own symbolic processions. At his hometown of Sidon in south Lebanon, about 250 students carried a symbolic coffin from a school built by and named after Hariri to a nearby mosque that he also constructed in honor of his father, Bahaaeddine Hariri.

A large Hariri portrait was placed on the Martyrs monument in Beirut's city square, once a killing field during the 1975-90 civil war. The bullet-riddled monument was restored only late last year.

The Beirut procession turned into a spontaneous anti-Syrian demonstration, with visibly enraged mourners shouting insults at Syrian President Bashar Assad (search) and demanding him to "remove your dogs from Beirut," a reference to Syrian intelligence agents, part of an overall contingent of 15,000 troops deployed in the country since 1976.

Syrian Vice President Abdul-Halim Khaddam (search), a close family friend, arrived at the mosque ahead of the funeral service, but did not take part in the procession. He was a frequent visitor of Hariri.

Absent from the procession were members of the Lebanese government — including President Emile Lahoud (search) — who were warned by Hariri supporters and relatives not to attend.

Many in Lebanon blame Syria for carrying out — or at least having a hand — in Hariri's killing. Syria denies the charge and has instead condemned the assassination.

Hariri resigned last year amid opposition to a Syrian-backed constitutional amendment that enabled his rival, the pro-Damascus Lahoud, to extend his term as Lebanon's president.

State-run Syrian television carried the funeral coverage live, picking up the feed from Lebanon's national TV station.

Syria deployed its forces to Lebanon during the civil war, but remained following the end of the conflict. Its continued presence is a source of frustration for many Lebanese, who oppose Syrian interference in their country's affairs, and for the international community, particularly Washington.

Interior Minister Suleiman Franjieh (search) suggested a suicide bomber backed by "international parties" may have killed Hariri, but said he could not confirm the theory. Media and expert speculation has suggested the bomb was placed in an underground drainage system.

The Associated Press contributed to this report.