WARNING - EDIT CONTAINS GRAPHIC CONTENT

Harrowing footage out of Syria on Tuesday is said to show Free Syrian Army rebels executing four loyalists to President Bashar al-Assad in an Aleppo schoolyard.

The men were first shown in a larger group, some of them with bloody wounds and bandages.

Four of them were then taken outside into the crowded yard.

A prolonged barrage of gunfire is then unleashed.

Drawing fierce condemnation from rights groups, Nadim Houry, of Human Rights Watch says the apparent executions were in breach of international law.

(SOUNDBITE) (English) DIRECTOR OF HUMAN RIGHTS WATCH IN THE MIDDLE EAST AND NORTH AFRICA, NADIM HOURY, SAYING:

"Extrajudicial executions are never justified, regardless of the identity of the victim. It is grave violation of international humanitarian law, of the Geneva conventions. It amounts to a war crime."

A member of the Syrian National Council said cruelty is not the answer.

(SOUNDBITE) (Arabic) MEMBER OF SYRIAN NATIONAL COUNCIL MAHMOUD OSMAN SAYING:

"Executions should not be happening in this cruel way. People should be given the right to defend themselves and then they can, be given the punishment they deserve. We revolted against injustice and against dictatorship."

The executions were said to have taken place as Assad's forces attacked residential neighbourhoods of Aleppo with artillery and from the air to try to drive out the rebels, who have reportedly maintained their foothold in the city.

Sarah Sheffer, Reuters