Arsal municipal chief Ali al-Hujairi and two of his companions were wounded in the attack, while another companion Mohammed Hasan al-Hujairi was killed, a statement from the army said, Xinhua reported.
According to the media, al-Hujairi and his companions were on their way back from a hostage swap that saw the exchange of Youssef al-Meqdad for several abductees who hail from Arsal, when they fell into an armed ambush on the road between Al-Labweh and Al-Nabi Othman.
The ambush was staged by "gunmen who were in four cars: a Cherokee and a Yukon SUVs and two Mercedes cars", the state-run National News Agency said, adding that Hujairi was wounded in the head.
As soon as the news of the ambush broke out, tensions soared in Arsal and a number of men fired their weapons in the air to condemn the attack.
The army was heavily deployed in Al-Labweh's square and on the road leading to Arsal.
A group calling itself 'The Brigades of the Four Martyrs' has claimed the responsibility of the attack.
The army confirmed the casualties and said the gunmen also abducted two Syrians who were in the convoy.
"Army units deployed in all Bekaa (Valley) regions, especially in northern Bekaa, have taken extraordinary measures to prevent any escalation," it said.
Troops are also conducting "a major search and investigation operation to identify and arrest the perpetrators and refer them to the relevant judicial authorities", the army statement added.