BEIRUT -- An explosion has killed or injured at least four Spanish members of UNIFIL and wounded several others, although reports trickling in are contradictory and confusing. UNIFIL spokespeople are currently not answering phones -- or the lines are busy. (The linked article says four Spanish soldiers were killed and four others wounded, but other stories give differing accounts.)

UPDATE: LBC and AP now report five Spanish troops killed, three wounded. Two bodies were charred beyond immediate recognition.

The explosion could have been an IED or car-bomb, as some reports indicate, or it could have been an unexploded mine, which litter the south of Lebanon. Obviously, if it's a mine that's a completely different story than if they were attacked. Indeed, Reuters says it was a landmine that killed four and wounded six.

UPDATE: Reuters is now reporting an IED detonated by remote control. And I spoke with a source familiar with the unexploded ordnance in the Khiam area and the United Nations' mine clearing operations. The source said if it was a mine, it would have had to be an anti-tank mine, which aren't as common in Lebanon as anti-personnel mines and that the Khiam area has been previously cleared of unexploded mines leftover from the various wars that have hit south Lebanon over the years.

Initial thoughts: The Spanish were probably in a BMR-600 armored personnel carrier, as shown here. Perhaps some readers might be able to provide some insight on landmine vulnerability of the BMR-600?

Also, groups claiming to be or affiliated with al Qaeda have long made threats against UNIFIL, but none have been carried out so far (assuming the explosion is a landmine and not a planted IED or something.) UNIFIL is hampered by its lack of good intelligence on the ground and a clear authority to pursue counter-terrorism activities. As such, Brookings notes, UNIFIL is forced to rely on the Lebanese security regime, which is relatively weak and hamstrung by the political situation. The current contretemps up north with Fatah al-Islam, which has pledged to expand its campaign outside the camp of Nahr el-Bared, further complicate matters. Brookings believes the threat of a "catastrophic" attack against UNIFIL is real, but not imminent, but today's blast, assuming it was an attack and not a tragic accident, could be a probing movement to gauge UNFIL's response and an attempt to affect its military posture and morale. Also, don't forget the homefronts for the contributor countries: Spain and France might go wobbly with their troop contribution should minor attacks picking off peacekeepers a few at a time become more common.

But why Spain? Spain, with 1,100 troops has the third largest contribution, behind France and Italy, and has been one of the more aggressive of the UNIFIL contingents, taking an active role in weapons confiscation and closely monitoring Hezbollah in the region. This has led to tensions with some Shi'ite villages, that are largely sympathetic to Hezbollah. Earlier this year, angry residents of a village just north of UNIFIL's deployment mobbed a jeep full of Spanish soldiers because the villagers thought they were spying against Hezbollah. In December, according to the Christian Science Monitor, Hezbollah planted several bombs against one of the Spanish patrols, "which had discovered an abandoned Hizbullah position with stockpiled mortar shells and rockets."

The area was formerly used by Hizbullah to launch attacks into the Shebaa Farms, an Israeli-occupied mountainside claimed by Lebanon. The trip-wire detonated bombs, all constructed from Israeli-made components, were planted by "experts with a lot of technical experience," an internal UNIFIL report on the incident said. "This situation suggests a change in the threat that UNIFIL may have to face," the report said.

After the bombs were discovered, Hezbollah told UNIFIL it was a local commander who was acting on his own and that he would be reprimanded and the incident would not be repeated.

In February, however, the Israeli army dismantled five linked bombs on a border road, claiming they were planted by Hezbollah the weekend before. Hezbollah denied it, saying the bombs were from before the July war last year and UNIFIL said there was no way to tell when the bombs were planted.

But Hezbollah is not the only -- or even most likely -- party behind the bombing. In fact, my hunch is they are the least likely to have done this. More likely are jihadis who are operating in solidarity with Fatah al-Islam up north (there were persistent stories circulating that UNIFIL's naval contingent was taking part in the bombardment of Nahr el-Bared), genuine al Qaeda elements or wannabes who want to impress al Qaeda leadership in order to gain admission. There has been so far no claim of responsibility, and the list of possible bombers is a long one.

More as information becomes available.