A roadside bomb hit a Spanish patrol vehicle of the United Nations Interim Force in Lebanon (UNIFIL) in southern Lebanon on Sunday, killing five Spanish peacekeepers and wounding five others.

A UNIFIL spokesman said the blast targeting the Spanish vehicle in southern Lebanon was caused by a roadside bomb and not a mine.

Previous reports said the explosion was probably caused by landmine or roadside bomb.

Local LBC TV quoted a security official based in southern Lebanon as saying that a bomb detonated at the side of a road, about six km north of the Israeli border town of Metulla.

Pan-Arab satellite TV al-Jazeera reported earlier that four Spanish peacekeepers were killed and three others were wounded when the explosion occurred as the Spanish patrol vehicle is driving on the road linking southern border towns of Marjayoun and Khiyam.

Shortly after the bomb attack, Lebanese Shiite group Hezbollah denounced the attack, calling it a "suspicious act."

The UNIFIL now has 13,000-strong troops in Lebanon, which has been fulfilling a peacekeeping task since last summer's Israel-Hezbollah conflict.

Lebanon's south is riddled with landmines, laid by both Israeli soldiers and Hezbollah militants.

However, the Fatah al-Islam militants holed up in the Palestinian Nahr al-Bared refugee camp also vowed to widen their targets of attack to the UNIFIL after the Lebanese army began an eradicating military offensive against the militant group.