Beirut this week sent forces to the northern city of Tripoli after fighting erupted between pro- and anti-Syrian factions in the city. The Cedar Revolution in Lebanon in 2005 brought an end to Syrian dominance over Beirut, though Syrian conflict is threatening to engulf its neighbors.
Jeffrey Feltman, U.N. undersecretary-general, told the U.N. Security Council that tensions were high in Lebanon because of the events in Syria.
"The situation in Lebanon has become more precarious and the need for continued international support to the government and the Lebanese armed forces increasingly important," he was quoted by CNN as saying during the closed-door meeting.
Arab governments last week called on their citizens to leave Lebanon following a series of kidnappings. The Daily Star newspaper in Lebanon reported that Syrian fighter jets were seen flying at a low altitude over the shared eastern border.
Victoria Nuland, a spokeswoman for the U.S. State Department, said the threat of spillover was "extremely concerning."