Violence erupted after funeral ceremonies Sunday for the intelligence chief whose assassination has plunged Lebanon into its worse crisis in years, threatening to ignite simmering sectarian tensions already aggravated by the war in Syria.
Leaders of the March 14 alliance have accused the Syrian government of killing Brig. Gen. Wissam al-Hassan, the head of the Internal Security Forces' information department in revenge for his role in exposing Syrian-led plots to plant bombs in Lebanon. He was a close friend and ally of Sunni political leader Saad al-Hariri, a central figure in Lebanon's anti-Syrian camp.
Hundreds of angry mourners surged toward the offices of the prime minister in downtown Beirut on Sunday after speakers at the funeral exhorted Sunnis to exact revenge for Hassan's death by toppling the Hezbollah-led government.
Lebanese security forces fired tear gas and bullets into the air to hold mourners back as what had been intended as a peaceful demonstration of outrage at the killing turned into an angry eruption of long-suppressed Sunni rage at the Shiite Hezbollah group's dominance in the country.
Sunni and Christian politicians have blamed Syria for the bombing that killed Hassan on Friday, accusing President Bashar al-Assad's regime of exacting revenge for Hassan's role in uncovering a plot ordered by Syrian officials to destabilize Lebanon by planting bombs around the country.
But increasingly anger is being directed at Hezbollah, as the dominant force behind the alliance running the government and as Syria's chief ally in the country.
"There is no God but God and Nasrallah is the enemy of God," chanted some of the thousands of mourners who gathered in downtown Beirut's Martyrs' Square for the funeral ceremonies, referring to the Hezbollah leader Hassan Nasrallah.
The Sunni leader Hariri, who lives in Paris, appealed to his followers to leave the streets and return home. "I want everyone to leave the streets now," he tweeted on his Twitter account. "Honoring Wissam al-Hassan does not happen this way. We are calling for peace, not calling for violence."
But amid reports that Sunnis elsewhere in the country had begun setting up roadblocks and burning tires, it was unclear whether Hariri's call would be heeded.
A statement issued Saturday by the March 14 alliance, in which Hariri is a key figure, had called for the resignation of Prime Minister Najib Mikati and his government, accusing it of doing "nothing but implement the policies of the killer Syrian regime."
Mikati told reporters he was ready to resign but said he had been asked by the president, Michel Suleiman, to stay on pending a resolution of the crisis.
"The government is not the issue," he said. "The government is going to resign sooner or later. Not now, but sooner rather than later. But we don't want to go into the unknown."
The crisis has heightened long-standing concerns that the conflict in neighboring Syria is spreading to Lebanon, whose factions have been polarized by the revolt against Assad's rule.
But the assassination has also revived festering grudges left unresolved by the upheaval of the past decade. The strife ended after Hezbollah fighters swept through the streets of the mostly Sunni West Beirut area of the capital in 2008, routing a fledgling Sunni militia formed by Hariri and asserting the movement's role as the country's most powerful military and political entity.
Sunnis have not forgiven Hezbollah for using against Lebanese citizens the weapons it is permitted to possess under the terms of the 1990 peace accord that ended Lebanon's 15-year civil war. Nor have they forgotten its conquest of areas traditionally deemed Sunni areas of influence.
Sunnis at a small protest rally organized by the March 14 coalition in downtown Beirut said the time had come to avenge both Hassan's death and the events of 2008.
"We won't accept humiliation anymore," said Anis Mikati, 24, who stood with his friends under a big, black banner inscribed in white with the Islamic declaration of faith often associated with al-Qaida. He denied affiliation with any group. "We are Sunnis, and we are ready to fight," he said.
A group of Christians waving the banner of the Lebanese Forces, a onetime militia faction in Lebanon's civil war, said they, too, were hoping for a fight to end Hezbollah's hegemony.
"We hope for a war to fix this country, because Hezbollah wants to control everything," said Ghadi Roukaiby, 16.
But the rally, held in Beirut's vast Martyrs' Square, was a shadow of the massive gathering there after Hariri's death, when as many as a million people turned out. The attendance Saturday called into question how far the Lebanese are prepared to go to express their anger at a time of deepening fears that the Syrian hostilities could ignite a region-wide conflict.
The U.N. special envoy for Syria, Lakhdar Brahimi, warned of the implications of allowing the Syrian war to rage unchecked during a visit to Beirut two days before the bombing.
"This crisis cannot remain confined within Syrian territory," Brahimi told reporters. "Either it is solved, or it gets worse . . . and sets [the region] ablaze."
Brahimi met in Damascus on Saturday with Syrian Foreign Minister Walid Moallem to discuss his proposal for a four-day cease-fire over the Muslim Eid al-Adha holiday that begins next weekend. He made no statements, but the Associated Press reported that he would meet with Assad on Sunday.
On the eve of Brahimi's arrival in Syria, activist groups said 84 civilians, many of them children, had died in a mass killing on the outskirts of the eastern city of Deir el-Zour. The British-based Syrian Observatory for Human Rights said 110 people were killed Saturday, including 37 members of the government security forces.
* Washington Post special correspondents Ahmed Ramadan and Suzan Haidamous contributed to this report.