Roads, squares and bridges were filled by supporters of Hezbollah, the Shiite militant party and militia; Amal, another Shiite party; and Christian groups that included Marida and Michel Aoun's Free Patriotic Movement, all determined to topple the government.

The mostly youthful crowds stretched from the Christian neighborhood of Gemayze in the east to government buildings ringed by concertina wire on the other side of downtown. Demonstrators filled alleyways and overpasses, and everyone seemed to be carrying a Lebanese flag, its red and white stripes framing a green cedar tree.

Distinguishing themselves by party, Hezbollah members draped the militia's flag about their shoulders, while Free Patriotic Movement supporters wore orange sweatshirts or baseball caps.

As night closed in, a crowd of about 2,000 people remained in the square, vowing to stay until the U.S.-backed government of Sunni politician Fuad Saniora resigns. What some observers call a "soft coup" attempt is the latest chapter in a political crisis that has seen assassinations, the exit of Syrian troops and war with Israel.

Iman Fakhiya and her sister-in-law, Amal Muhammad, wrapped themselves in a tiger-striped fleece blanket and settled in for what could be an extended siege of Lebanon's government.

"If they need a week, we'll sit here for a week," said Fakhiya as Muhammad huddled next to her in the chilly evening. "If they need more (time), we'll stay more."

Nearby, Muhammad Obaid echoed a common complaint of the opposition movement now called the March 8 coalition. "The real problem with this government is that they did not stand with us during the war" between Hezbollah and Israel, he said.

On July 12, Hezbollah, which receives support and arms from both Syria and Iran, captured two Israeli soldiers and killed eight more in a cross-border raid. The move prompted a massive retaliation by the Jewish state that turned into a 34-day war. In the aftermath, Lebanon tallied its losses -- more than 1,000 Lebanese dead, most of them civilians, and the country's infrastructure and industries devastated. Hezbollah leaders say Saniora's government quietly hoped for the Shiite group to lose the war so that it no longer would be a potent political opponent.

Instead, Hezbollah emerged from the conflict stronger than ever, demanding more power for itself and its allies. After six Cabinet ministers from Hezbollah's political bloc resigned, and Industry Minister Pierre Gemayel, a Christian, was murdered on Nov. 21, the March 8 forces hoped to force the resignation of the Saniora government and the calling of new elections -- which they feel they can win.

The stakes are high for all sides, said Reva Bhalla, director of global analysis for Strategic Forecasting Inc., a research firm is in Austin, Texas. Hezbollah's "whole overall intent here is to completely paralyze the government and get them to accede to their demands," she said. "But they were very concerned things would spiral out of control."

Some analysts say Hezbollah leaders fear that foreign intelligence agents -- including those from Syria -- will provoke a violent confrontation. So far, with a few minor exceptions, Hezbollah seems to have avoided that.

Friday's protesters were for the most part friendly and respectful of a call by Hezbollah leader Hassan Nasrallah not to damage property or resort to violence. One group of young toughs did celebrate Gemayel's murder, chanting, "Congratulations to Pierre, when is Geagea next?" Samir Geagea is the leader of the Lebanese Forces, a Christian political party that is particularly hated by Lebanese Shiites.

Only after a reporter asked them why they were chanting such things did a Hezbollah security guard intervene. "They are not polite," the guard said as he pushed the reporter away roughly. "I don't want you talking to people who aren't polite."

As night fell, trucks carrying portable toilets and water tanks arrived while tents were set up in the downtown Martyrs' Square.

The demonstrators closed off streets around the Grand Serail, the prime minister's headquarters where Saniora and his Cabinet were holed up. Soldiers told the crowds to allow government officials to enter and leave the building, but members of the Hezbollah security forces said they took orders only from Hezbollah commanders. It took phone calls from parliament speaker Nabih Berri, head of the Amal party and a staunch Hezbollah ally, to defuse the situation and get the streets open again.

While such actions might be the work of hotheads, they give weight to official claims of pro-government factions that Hezbollah and its allies are trying to oust Saniora.

"This is an attempted coup, but we will remain strong," Progressive Socialist Party head Walid Jumblatt told a news conference shortly before the protests began.

Meanwhile, Stratfor's Bhalla says there is a good possibility that Saniora will resign. "The only question is: Who would replace him," she said. "There aren't any strong figures in the Sunni blocs."

Saniora, however, has vowed not to step down.

"We will not allow a democratic government to be toppled, or its institutions," he said in a televised address. "Nor will we allow a state within a state. We are the legitimate government and responsible for all Lebanese."

But for Fakhiya, it is only a matter of time before the prime minister is gone, and she vowed to stay in the protesters' encampment.

"It doesn't matter," she said referring to the cold as she pulled a blanket tighter to her body. "It's not a problem as long as we achieve what we want."