"This criminal act aims at threatening the country's security and stability," Sleiman said in a statement.

Parliament Speaker Nabih Berri also voiced his concern over the attack on a highway leading to the southern city of Sidon which left six Italian peacekeepers wounded. Two Lebanese bystanders were also slightly wounded.

"We are condemning this terrorist crime, as we offer our condolences to the UNIFIL leadership and especially the Italian unit, hoping for the speedy recovery of those wounded," Berri said in the statement, adding that Lebanon's state of political paralysis threatens the country's security and spreads chaos.

Meanwhile, caretaker Prime Minister Saad Hariri warned of any attempts to use Lebanese territory “to send messages to the international community and specifically to UNIFIL in south Lebanon.”

“We hope that the international forces resume their work according to [United Nations Security Council Resolution] 1701. The Lebanese government considers [the resolution] a basic rule for preserving stability and preventing violence in the area," Hariri said in a statement.

Resolution 1701 was drafted to end the 2006 war between Lebanon and Israel. The UNIFIL peacekeeping presence was beefed up in the wake of the conflict and is mandated with maintaining a cessation of hostilities, as well as monitoring the implementation of 1701.

Prime Minister-designate Najib Mikati also condemned the bomb attack, praising the U.N. for preserving stability and security in south Lebanon.

Mikati's remarks came during a telephone conversation with U.N. Special Coordinator for Lebanon Michael Williams, a statement from his press office said.

UNIFIL has around 12,000 troops and naval personnel in Lebanon after its expansion under Resolution 1701.

The attack was the first was since January 2008, when a roadside bomb struck a U.N. vehicle traveling along the same coastal highway, lightly wounding two peacekeepers.