The United Nations condemned on Friday the killing of a wounded Arab terrorist by an Israeli soldier in the city of Hevron a day before, after a video of the death was spread online.

"I strongly condemn yesterday's apparent extra-judicial execution of a Palestinian assailant in Hebron in the occupied West Bank," UN Special Coordinator for the Middle East peace process Nickolay Mladenov said in a statement.

"This was a gruesome, immoral and unjust act that can only fuel more violence and escalate an already volatile situation."

Mladenov called on the Israeli authorities to "swiftly bring to justice" the soldier involved in the incident.

The Israeli army on Thursday arrested the soldier caught on video shooting a wounded terrorist in the head as he lay on the ground after stabbing another soldier.

The viral video clip, which was recorded by the far-left B’Tselem organization, has been disputed by witnesses on the scene, who argue that the video, which was taken at a distance and lacks audio, misrepresents the situation.

The soldier claimed that the terrorist appeared to be wearing a suicide bomb vest, and he feared the terrorist was trying to activate the explosive device.

A witness told NRG that there indeed was concern among those on the scene that the terrorist was carrying a bomb.

An attorney representing the soldier noted that despite the warm weather, in the video the terrorist can be seen wearing a heavy sweater – often a sign of a concealed bomb vest.

On Friday a second video emerged taken at the scene of the terror attack, in which several people on site express concern that the terrorist “looks like he has an explosive pack," warning others to keep clear of him until a bomb sapper arrives.

Prime Minister Benjamin Netanyahu criticized the soldier, saying that his behavior was not in keeping with the army's values. Defense Minister Moshe Ya'alon vowed that the incident was being treated with "utmost severity."

Former foreign minister Avigdor Liberman defended the soldier, saying it was "hypocritical and unfair to gang up against the soldier."

"Better a soldier who makes a mistake but stays alive than a soldier who gets killed by a terrorist because he hesitated," he said.

AFP contributed to this report