Beirut police said four people were killed and more than 150 injured after fighting between supporters of the Sunni government and Shiite opponents at Beirut's Arab University spread around the city, the BBC reported Friday.
The violence was halted when the Lebanese army arrived and fired shots into the air.
CNN reported the curfew was imposed from 8:30 p.m. Thursday until 6 a.m. Friday. The news network said no violence had been reported early Friday.
The violence Thursday spread from the college campus when supporters of the Shiite Hezbollah movement called other members of the organization for assistance and residents of a Sunni neighborhood moved to assist government supporters, the BBC said.
"We are witnessing scenes that remind us of the civil war," said Parliament Speaker Nabih Berri, who supports the government.