The fighting in the country's second largest city began overnight Wednesday, when grenades exploded along a main road separating a pro-government Sunni Muslim district from one that is home to mostly Alawite supporters of the Hezbollah opposition.
The Bab el-Tabaneh and Jabal Mohsen districts were also caught up in fighting between opposing factions on June 22 when 10 people were killed and 55 injured.
In May, Lebanon resolved an 18-month political crisis after the Western-backed coalition and the opposition reached an agreement brokered in Qatar.
Prior to the deal, violent clashes that broke out between the factions in early May left more than 80 people dead and about 200 wounded.
Lebanon's political stalemate began in late 2006 when pro-Syrian ministers quit the cabinet of Prime Minister Fouad Siniora during a power struggle. The U.S.-backed government and the Hezbollah-led opposition spent more than a year deadlocked and unable to elect a president.
