The UN high commissioner for human rights has called for an investigation into allegations that Syrian rebels executed dozens of government soldiers captured after a battle near Aleppo.

Navi Pillay said that images of the killings in Khan al-Assal in July were deeply shocking, and highlighted yet again the need to ensure those responsible for violations of international humanitarian law and international human rights law on all sides are made to account for their crimes.

Pillay said that captured or wounded soldiers should be treated humanely and in accordance with international law.

"Opposition forces should not think they are immune from prosecution. They must adhere to their responsibilities under international law," she said.

Footage taken by opposition forces in Khan al-Assal, a district in rural Aleppo, was posted on the internet between 22 – 26 July.

One video apparently shows government soldiers being ordered to lie on the ground, while another shows several bodies scattered along a wall and a number of bodies at an adjacent site.

"These images, if verified, suggest that executions were committed in Khan al-Assal," said Pillay, "There needs to be a thorough independent investigation to establish whether war crimes have been committed. And those responsible for such crimes should be brought to justice."

The high commissioner said her team in the region was investigating the reports, and had examined the videos and collected accounts from people in Aleppo. Their early analysis had identified two men not in uniform who were alive in one video but were among the dead bodies in another.

Another video shows bodies being collected by members of the Red Crescent and Free Syrian Army medical doctors. There were several other videos showing the bodies of dead government soldiers scattered around town, most of whom appeared to have been shot in the head.

Pillay said: "Based on the analysis by my team to date, we believe armed opposition groups in one incident – documented by a video – executed at least 30 individuals, the majority of whom appeared to be soldiers."

There have been reports that the overall number of dead in Khan al-Assal was much higher and the Office for the high Commissioner for human rights was continuing to investigate the circumstances and scope of the killings.

Khan al-Asal has also been cited as the site of the use of chemical weapons by either opposition or government forces. The OHCHR team also received information from a reliable source that opposition fighters are still holding government officers and soldiers captured in Khan al-Assal.