(Adds U.N. Security Council condemnation, details on bomb)
By Yara Bayoumy
MARJAYOUN, Lebanon, June 25 (Reuters) - U.N. peacekeepers will pursue their mission in south Lebanon despite a car bomb that killed six members of a Spanish battalion, their commander said on Monday.
The attack on a Spanish patrol on Sunday was the first deadly assault on the U.N. Interim Force in Lebanon (UNIFIL) since last year's war between Israel and Lebanese Shi'ite Hezbollah guerrillas backed by Iran and Syria.
"This attack has made UNIFIL more committed to fulfil its mission in southern Lebanon," said Major-General Claudio Graziano, commander of the 13,000-strong force.
The bombing presents another challenge to the Western-backed Beirut government, locked in a paralysing political conflict with the Hezbollah-led opposition and shaken by a series of bombings, as well as battles with al Qaeda-inspired militants.
The bombing, which Hezbollah condemned, occurred even though UNIFIL had gone on higher alert after the Lebanese army began fighting Sunni Islamist militants in the north last month.
No group has claimed responsibility, but the Fatah al-Islam group battling the army in the Palestinian refugee camp of Nahr al-Bared had threatened UNIFIL earlier this month.
UNIFIL, operating alongside about 15,000 Lebanese troops sent to the south after the July-August war ended, has reported few problems with Hezbollah, which keeps its arms out of sight.
It has seen Sunni militants as a greater peril since al Qaeda number two Ayman al-Zawahri threatened attacks last year.
ALARM BELLS FOR UNIFIL
Timur Goksel, a former UNIFIL spokesman, said he saw the bombing as a "solidarity operation" linked with the Nahr al-Bared fighting, perhaps carried out by a group promoting itself as a "candidate for al Qaeda membership".
Spanish Defence Minister Jose Antonio Alonso flew to Lebanon to attend a religious ceremony for the slain soldiers at their base in Marjayoun, and bring home their bodies.
UNIFIL troops with sniffer dogs combed fields near the site of the blast for clues. Conflicting reports said the 40-50 kg (90-110 pound) bomb had been detonated by remote control or by a suicide driver.
Goksel said the attack sharpened a dilemma for UNIFIL, which must balance the need to protect its troops against its goal of fostering good relations with the public.
"The problem is it might change the whole attitude of some of the contingents. They are going to be much more nervous than before, more aggressive-looking -- and act that way ...," he said. "It's going to be a serious setback, unfortunately."
Residents in Marjayoun and nearby Khiyam said they appreciated the UNIFIL presence, not least because of the money the troops spend in local shops and restaurants. Some said they feared the attack on the Spanish troops would not be the last.
"I'm expecting that it will happen again, next time against the French or the Italians," said Ahmed Hijazi, 30, in his empty cafe on the main road through the Christian town of Marjayoun.
The U.N. Security Council condemned the "terrorist attack" and reaffirmed its support of the Lebanese government and army. U.N. Secretary-General Ban Ki-moon also called for the bombers to be brought to justice.
"Targeting of UNIFIL is in fact an attempt to undermine peace and security in the region," his spokesperson said.
In Beirut, Prime Minister Fouad Siniora's anti-Syrian cabinet decided to ask the U.N. Security Council to prolong UNIFIL's mandate, which expires in August, for another year.
UNIFIL has now suffered 266 fatalities since it was set up after a 1978 Israeli invasion.
(Additional reporting by Nadim Ladki in Beirut, Karamallah Daher in Marjayoun and Claudia Parsons at the United Nations)