Violent clashes broke out Sunday between Shiite and Sunni Muslims in the capital, leaving one man dead from gunshot wounds at a time when tensions threaten Lebanon's fragile sectarian and political balance.

The death was sure to inflame sectarian divisions as both the Shiite Hezbollah militant group and the U.S.-backed government it has vowed to topple refused to retreat.

Hezbollah for the third day continued its ongoing street protests aimed at forcing Prime Minister Fuad Saniora to resign, as the Sunni leader, emboldened by Arab and international support for his government, pledged to stay in office.

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Police officials said Ahmed Ali Mahmoud, a 20-year-old Shiite Muslim, was shot and killed during a clash between Shiites and Sunnis in the West Beirut neighborhood of Tarik Jdideh. The officials spoke on condition of anonymity because they were not allowed to speak tot he press.

The clash occurred as a group of Hezbollah supporters were returning from the downtown protest and passed through the predominantly Sunni neighborhood. The police officials said the two sides threw stones at each other before the clash before shots were fired.

In a separate clash in another West Beirut neighborhood, a fist fight and stone-throwing clash erupted between groups of Shiites and Sunnis, and several shops were set on fire and the windows of at least one car smashed. Army troops fired smoke bombs to disperse the crowd, and at least 10 people were slightly injured in the stone-throwing, the officials said.

The political crisis between Hezbollah and its pro-Syrian allies and Saniora's anti-Syria block has raised fears of violence between the two rival factions. The tension skyrocketed after a Christian anti-Syrian minister was assassinated last month, and pro-Hezbollah supporters began staging the ongoing sit-in in downtown Beirut about 50 meters (yards) away from Saniroa's headquarters on Friday.

Hezbollah, which was emboldened after its summer war against Israel, first called for the mass protests after six pro-Hezbollah ministers resigned from the Cabinet last month. Saniora and his anti-Syrian parliament majority had rejected the group's demand for a national unity government that would effectively have given it and its allies veto power.

Saniroa's government is largely backed by Sunni Muslims and Christians who oppose involvement in the country's affairs by neighboring Syria, which was forced to end a nearly three-decade military occupation last year.

Hezbollah, an ally of Syria that is backed by many Shiite Muslims and some Christians, contends the fight is against American influence, saying the United States now dominates Lebanon in the interests of Israel.

Earlier Sunday, amid the sounds of revolutionary and nationalist songs blaring from protesters' tents, a Mass in memory of assassinated Industry Minister Pierre Gemayel was held at Saniora's office.

But a few meters away, a rival Mass organized by supporters of Christian leader and Hezbollah ally Michel Aoun was held at the St. George Cathedral.

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From his office, Saniora vowed to continue as premier and asserted that the protests would not achieve their goal. He hinted that the anti-Syrian coalition backing him might stage counter protests if the opposition's sit-in drags on.

"A solution to any problem does not come through the street because this means might trigger a counter-means and therefore, we will not reach any result," Saniora told reporters.

He warned that any attempts by Hezbollah's supporters to storm his office, ringed by hundreds of police and soldiers, tanks and armored vehicles, would lead to "a major and serious problem." The prime minister appeared to be cautioning against the possibility of open fighting between Sunnis and Shiites.

Pro-Hezbollah speakers, meanwhile, vowed to continue their street protests and campaign to remove Saniora from power.

"We will not leave until the government is changed," former interior minister Suleiman Franjieh, a staunch ally of Syria, told the crowd. He said the protesters were ready to celebrate Christmas, the New Year and the Muslim feast of Eid al-Adha in tents in central Beirut to pressure the government into resigning.

In Jerusalem, Israeli officials on Sunday warned that the fall of Saniora's moderate government could lead to the establishment of an Iranian proxy state on Israel's northern border and increase the probability of war between the two nations.

Arab League Secretary-General Amr Moussa said Arab countries could not afford to adopt "a spectator's stand" on the fast-moving developments in Lebanon.

"The Arab world, cannot ... sit and just watch Lebanon. Lebanon is an important component of Arab nations. The stability in Lebanon and moving towards a solution that would bring about a sure future for the country is one of our concerns," Moussa said after arriving in Beirut for talks leaders from the rival factions.

Following a meeting with Saniora, Moussa described the situation as "dangerous" and said he was trying to work with all the parties to try and restore unity.

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