Israel's military says it is investigating video footage, filmed through the scope of a rifle, allegedly catching soldiers cheering the shooting of an apparently unarmed Palestinian.

The video, which went viral online and featured prominently on Israeli TV, was denounced by Israeli politicians.

The military said the shooting, seemingly on the Israeli-Gaza border, probably occurred a few months ago.

The case comes at a time of heightened tensions over Gaza.

Israel has faced mounting criticism for shooting dozens of Palestinian, many fatally, during clashes at protests along the border in the past two weeks.

Israel has defended its actions, saying it has only used live fire against individuals trying to breach the border fence, or those using weapons or explosives.

'Horrifies the mind'

In the video broadcast on Monday, three men are seen nearing a barrier or fence. The crack of an apparent gunshot is heard and one of the men, who had been standing still and appeared to be unarmed, falls to the ground.

A voice is heard to exuberantly declare in Hebrew: "Wow, what a video. Yes! Son of a bitch! What a video!"

A crowd of people are then seen rushing to retrieve the man who was shot. His condition is not clear.

The video first appeared on Israel Channel 10 television and was widely shared online, drawing shocked reactions.

Israeli Arab MP Ayman Odeh said in a tweet that the video "horrifies the mind". "Calls of joy at taking a life and what appears to be the execution of someone who did not threaten anyone," he added.

He called for the alleged culprits to be put on trial.

The alleged incident was also denounced by Israeli politicians on the right and left.

Yehuda Glick, from the ruling Likud party, called it a "very hard video to watch. Disturbing and disappointing."

Others though cautioned against passing judgment on the evidence of the video clip alone.

"Was it so boring in this country over the last day that this video needs to receive such exposure?" asked Public Security Minister Gilad Erdan.

"To take a situation from the battlefield, when soldiers are under stress and explosive devices are being thrown at them and attempts are being made to infiltrate [the border], and to take their human response and judge them from the armchairs in Tel Aviv?"

Prominent Israeli human rights group B'Tselem said it had little faith in the Israeli military investigation.

"Israeli policymakers & military officials' professed shock & promise to investigate are lip service, their 'thorough investigation' will be whitewashing yet again," it tweeted. "They are the ones supporting manifestly illegal commands ordering soldiers to shoot people who pose no threat."