BEIRUT - A convoy carrying members of Hezbollah was hit by a roadside bomb near the Lebanese-Syrian border on Tuesday, wounding three of its officials in the third attack on the Shi'ite militant group since May, security sources said.

The injured men were Hezbollah security officials traveling in a convoy of two vehicles heading towards Syria. A barrage of gunfire hit the convoy after the blast, security sources said.

It was not immediately clear who was behind the attack, but Syrian Sunni rebel groups have threatened to strike Hezbollah in Lebanon following the group's military intervention in Syria on the side of President Bashar Assad.

The attack comes a week after a car bomb injured more than 50 people in a southern Beirut suburb controlled by Hezbollah, one of the most powerful political and military forces in Lebanon. In late May, rockets were fired at a Hezbollah area of southern Beirut.

Pictures from the scene showed black smoke rising from the targeted cars. The windscreen of one of the vehicles had several bullet holes.

A truck driver who witnessed the attack said he heard an explosion and the Hezbollah vehicle, a GMC sport utility vehicle, slowed to a halt.

Three or four gunmen arrived in another car and started firing at the GMC. "Then they got back in their car and fled," the driver said.

Several small roadside bombs have been set off near the Syrian border crossing in recent months.

Lebanon, which fought its own 15-year civil war, is struggling to stay on the sidelines of its larger neighbour's bloody conflict. Car bombs and sporadic clashes between groups supporting opposite sides of Syria's war have become increasingly common.

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