A roadside bomb blew up a UN vehicle near the southern Lebanese port city of Sidon on Monday, wounding at least three peacekeepers, Lebanese security and witnesses said.
The nationality of the peacekeepers was not immediately clear.
"It was a roadside bomb that hit a UN troop carrier on a bridge in Sidon. We are still checking what their nationality is," a Lebanese security official said.
A similar attack near Sidon in May wounded six Italian peacekeepers, prompting Italy to look into reducing its peacekeeping contingent in Lebanon.
UNIFIL has about 12,000 troops and naval personnel in the country after its expansion under UN Security Council resolution 1701 that halted the 2006 Israel-Hezbollah war in southern Lebanon.
UNIFIL operates alongside 15,000 Lebanese army troops who are deployed in the south to keep peace near the frontier with Israel and prevent weapon transfers in an area that is a stronghold of Hezbollah militant group.