The 2005 assassination of former Lebanese Prime Minister Rafik Hariri sparked a Lebanese revolution that forced Syria to end its long-term dominance over affairs in Beirut. The ongoing conflict in Syria has sparked fears the crisis could spill across the border, however.
Security forces told The Daily Star newspaper in Lebanon that Syrian helicopters were seen flying at low altitude along the eastern Lebanese border.
Lebanese forces deployed to the northern city of Tripoli to oversee a cease-fire agreement brokered between pro- and anti-Syrian factions in the region. The Lebanese report states some groups haven't agreed to lay down their weapons, however.
At least 12 people, including one soldier, were killed and another 76 people were injured by fighting in Tripoli.
The military, in a statement, called on Lebanese leaders "not to intervene on the ground" in order to keep rivalries from escalating.
Arab governments last week called on their citizens to leave Lebanon given tensions in the region. Victoria Nuland, a spokeswoman for the U.S. State Department, said Lebanese forces were commended for their efforts to contain the violence.
"It's obviously very worrying and a bad example of negative spillover," she said.