The UN has expressed concern after footage emerged apparently showing Iraqi troops beating and executing three Islamic State (Isis) prisoners. The video was reportedly shot in Mosul, where Iraqi troops have now recaptured the east of the city and are fighting to retake the west from the Jihadists, who have occupied the country's second largest city since 2014.

The video shows three Isis prisoners being dragged through the streets as they plead for their lives. One man, who seems to be injured and sitting with his back to a car, is dragged by his foot along the rough track as he howls with pain and other soldiers kick him in the head. Another man is also beaten as shots ring out in the background. Finally all of the men are gunned to death.

In a statement, the UN Assistance Mission for Iraq (UNAMI) "calls on the government of Iraq to investigate a video report circulating on social media sites which purportedly shows the brutal mistreatment and murder of at least three captured ISIL [Isis] members in a retaken area between Intisar and Karma neighbourhoods of east Mosul at the hands of what appears to be Iraqi Security Forces Personnel."

In his weekly news conference, Iraqi prime minister Haider al-Abadi hailed the "unmatched heroism" of all security force factions in the bid to retake Mosul. "Daesh has quickly collapsed and no one expected such collapse," al-Abadi was quoted as saying by the Mail Online. "The heroism of our security forces was behind Daesh's [an Arabic acronym for Isis] defeat."

Although Isis' resistance has crumbled quicker than expected in the east of the city, the fight for western Mosul is expected to take much longer. UNAMI says it is now concerned for an estimated 750,000 civilians trapped in the west when fighting begins there in earnest.

Lise Grande, Humanitarian Coordinator for Iraq, said: "The reports from inside western Mosul are distressing. Humanitarian partners are unable to access these areas but all the evidence points to a sharply deteriorating situation.

"The prices of basic food and supplies are soaring. Water and electricity are intermittent in neighbourhoods and many families without income are eating only once a day. Others are being forced to burn furniture to stay warm."