The Lebanese Army is on alert, after rival political factions exchanged gunfire in West Beirut.
Similar Sunni and Shi’ite tensions threatened to boil over into civil war last year.
The army said it would open fire against any armed person found on the streets.
The latest violence comes off the back of recent elections in Lebanon which saw a US-backed coalition, led by Saad al Hariri, defeat the Iranian backed Hezbollah.
Last year in clashes, Shi’ite Hezbollah fighters routed Hariri supporters and their allies in Beirut and the mountains to the east.
As tensions rise again, Hariri is set to begin consultations today to try to achieve his pledge of forming a national unity government.