US investigates video in which Syrian rebels 'decapitate' young boy

The US is investigating a video which purportedly showing Syrian rebels beheading a child.

Fighters from the Syrian insurgent group Nour al-Din al-Zinki - who have previously received backing from the US - reportedly captured the young boy near Aleppo, where it is one of main opposition factions fighting the Syrian regime of President Bashar al-Assad .

An earlier video appears to show six of fighters bragging about capturing the boy, who they claim was a fighter from a pro-government faction int he area.

The footage shows one fighter holding him by his hair while another rubs and slaps his face before giving a thumbs up to the camera.

A second video released later purportedly shows one of the fighters beheading the boy.

US State Department spokesman Mark Toner said Washington was seeking more information on what he described as “an appalling report”.

“If we can prove that this was indeed what happened and this group was involved ... it would give us pause about any assistance or any further involvement with this group,” he told reporters.

Nour al-Din al-Zenki said it would investigate the footage, calling the incident an "indiviual mistake" that did not represent the group at large. The group said everyone involved in the violation was arrested and are being investigated.

The Syrian government denounced the “repulsive crime” against an innocent child in a statement to the United Nations, saying the boy was a Palestinian from the Palestinian refugee camp of Handarat on the edge of Aleppo.

Nour al-Din al-Zenki previously received financial aid from the United States in a CIA-run programme intended to support moderate rebel groups in Syria.

According to a report by Amnesty International, the group has been involved in the abduction and torture of journalists and humitarian workers in Aleppo during 2014 and 2015,

Over 250,000 people have died in the Syrian civil war since it began in 2011.