The attack on a U.S. embassy vehicle that killed four people last week represents a dangerous widening of political violence that includes international targets, and shows how al Qaeda-inspired extremists are attempting to push the politically deadlocked country toward civil war, some analysts say.

"Al Qaeda is now unleashed in Lebanon and they are here to stay," said Ahmad Moussali, professor of political science and Islamic studies at the American University of Beirut. "Al Qaeda thrives in civil war and chaos. International players should be very careful in Lebanon."

With parliament unable to agree on a successor to Emile Lahoud, Lebanon has been without a president since Nov. 23. It is the culmination of a yearlong political crisis that has seen the political opposition led by the Shiite group Hezbollah attempting to bring down the U.S.-backed government.