Supporters of the government and Hezbollah clashed at a Beirut university campus Thursday, battering each other with sticks, stones and even pieces of furniture in new violence spilling over from Lebanon's political crisis.

Four people, two of them students, were killed, Arab media reported.

Black smoke poured into the sky from cars engulfed in flames as armored vehicles full of troops moved in to try to keep the two sides apart. But the riot spread into the nearby streets around Beirut Arab University as supporters of each side flowed in to join the fight, carrying makeshift weapons — chair legs, pipes, garden tools, sticks and chains.

After a three-hour battle, most rioters dispersed, and the military declared a nighttime curfew in an attempt to put down sporadic scuffles that continued in the area.

The university melee marked the third straight day of violence as Lebanon's political power struggle between the government and the Hezbollah-led opposition moved into the volatile streets. There, the conflict has taken on an increasingly dangerous sectarian tone and many fear it could spiral out of control and push the country into civil war.

In the evening, Hezbollah leader Sheik Hassan Nasrallah sought to rein in his followers.

"It is a religious duty. All must ... leave the streets and remain calm and restrain themselves and leave the arena for the army and the security forces to shoulder full responsibility to control the situation," Nasrallah said in an audio message broadcast on Hezbollah's Al-Manar TV and other channels.

The new violence came as Prime Minister Fuad Saniora was in Paris at a conference of donor nations that promised more than $7 billion in aid to rebuld after this summer's devastating Hezbollah-Israel war.

The money aims to boost Saniora's government, but the chaos at home has raised doubts whether his government can properly use the money.

The fight at the university deepened fears that the leaders of Lebanon's factions are weilding less control over their followers. Students said it began with an argument in the university cafeteria between pro-government Sunni students and Hezbollah and other anti-government supporters.

They said university security broke up the fight, but the Sunni supporters encircled the campus, located in the mainly Sunni Muslim neighborhood of Tarik el-Jadideh.

Hezbollah supporters called in help, and residents from the surrounding Sunni neighborhood joined in — and the fight spiralled into a free-for-all, spilling into the surrounding streets. Rioters set fire to cars and tires and smashed vehicle windows. Young men carrying sticks and wearing hard hats came in and pelted each other with stones. Some flung pieces of furniture.

Amid the brawl, some students claimed they came under fire from snipers nearby. Mohammed Abdul-Sater, a 21-year-old Shiite student, said he saw at least three people wounded by the gunfire.

"We are afraid about the future of the country," he said. "We are afraid about civil war," said Abdul-Sater.

Hezbollah's al-Manar TV reported two of the Shiite group's supporters were killed. Security officials could nto confirm the death but reported 17 people injured. Other TV stations reported that about 25 people were hurt.

Army troops fired tear gas and volleys of live automatic rifle fire into the air and lined up to disperse the crowd, a process that took several hours in the quickly moving fights.

Seeking to prevent the trouble from spreading, Hezbollah's leadership issued a statement on al-Manar accusing pro-government factions of provoking the clashes and calling on its supporters to get off the streets to "avoid strife being inflamed" by government supporters.

Saad Hariri, leader of the parliamentary majority and the leading Sunni opponent of Hezbollah, also urged his supporters to exercise restraint.

This week's violence has been a dramatic escalation in the Hezbollah-led opposition's attempts to oust the Saniora government. The opposition has staged two months of demonstrations and sit-ins ini an attempt to push him out, but the prime minister has refused the opposition's demand for veto-wielding share of the Cabinet.

The crisis turned violent on Tuesday, when a general strike called by the opposition sparked clashes with government supporters around the country that killed three people. On Wednesday, gunbattles broke out for a second straight day in the northern city of Tripoli.

Lebanon fought a 15-year civil war between its Christian and Muslim communities, ending in 1990. The current political crisis has divided the country along different lines — with Sunnis largely backing Saniora, Shiites behind Hezbollah, and Christians divided between the two camps.