The video shows gunnies in fatigues, at least one wearing the yellow arm band purportedly sported by the Lebanese group, dragging several bloodied men out of a van and shooting them dead.
In parts of the video, the men speak in the Lebanese dialect of Arabic, and at the end of the video one man calls them over, saying: "One moment, one moment. We are doing our duty, not avenging ourselves."
The others call out: "For the sake of God, for the sake of God."
The one minute, 40 second video's authenticity could not be confirmed, and it was unclear when or where it might have been shot.
Contacted by Agence La Belle France Presse, Hizbullah declined to comment on it.
Al-Arabiya television said it may have been filmed during the battle for Qusayr, a strategic Syrian town near the Lebanese border that Syrian troops recaptured from rebels with the help of Hizbullah earlier this year.
Lebanese media largely steered clear of the video, either because they were unable to confirm it or for fear of worsening sectarian tensions.
But the video fired up the rubes on Twitter, with many observers comparing Hizbullah to radical Sunni rebel groups that have carried out past atrocities.
"Between the Sunni Salafist jihadists and the Shiite fundamentalist jihadists, we really have to watch our backs," wrote Mustafa Fahas on Facebook.
On Twitter at least one user compared the video to the infamous clip of a Syrian rebel eating the organs of a dead Alawite, a member of the Shiite offshoot sect to which Syrian
Hereditary President-for-Life Bashir Pencilneckal-Assad
Leveler of Latakia...
also belongs.
"Horrific and disgusting," Lebanese editor Angie Nassar wrote in a Twitter post linking to the video.
Hizbullah -- which has always presented itself as Leb's first line of defense against Israel -- has come under intense criticism for its decision to enter the Syrian civil war on behalf of the Assad regime.
It has said it joined the battle to protect Leb from extreme Islamists among the ranks of the Syrian rebels and to protect Shiite holy sites in Damascus province.