Five peacekeepers with the U.N. Interim Force in Lebanon were injured in southern Lebanon. UNIFIL said the act was "vile and despicable" and undermined regional stability and peace.
French Foreign Minister Alain Juppe during the weekend told French media it was possible the attack came from Syria.
Jihad Makdessi, a spokesman for the Syrian government, was quoted by the official Syrian Arab News Agency that Juppe was grasping at straws.
"It seems that the French foreign minister is now adopting conspiracy theories, which he accuses others of doing," he said.
UNIFIL said it had a team on-scene with the Lebanese military investigating last week's attack, the third such incident this year.
UNIFIL added a rocket caused serious injuries to a citizen in southern Lebanon when it struck her home last weekend.
"There is clearly a need for further enhancing security control in the area," UNIFIL Commander Maj. Gen. Alberto Asarta Cuevas said in a statement. "Recent efforts by certain elements have been directed at destabilizing the area and we simply cannot allow such acts of violence that endanger the safety of the local population and the security of southern Lebanon."
There were no claims of responsibility for the most recent attack.