Children as young as nine have been used as human shields, sexually assaulted and tortured by forces loyal to Syrian President Bashar al-Assad, according to a United Nations report.

Its annual report on children and armed conflict states that government forces, including the Syrian Armed Forces, the intelligence forces and the Shabbiha militia have all targeted children.

Some have been tortured for information about opposition forces and others have been placed on tanks and buses to prevent rebel groups from opening fire.

The report said: “Children as young as nine years of age were victims of killing and maiming, arbitrary arrest, detention, torture and ill-treatment, including sexual violence, and use as human shields.”

The chilling document also describes how former members of the Syrian Armed Forces admitted that on occasions they have been ordered to fire arbitrarily into unarmed groups of civilian protesters, with their commander knowing they contained women and children.

It said: “[One member], during protests in Tall Kalakh in December 2011, was given an order by his commander to shoot without distinction.

“During the armed break-up of the demonstrations, the witness saw three girls between approximately 10 and 13 years of age who had been killed by the Syrian Armed Forces.

“In another similar incident in Aleppo in the fourth quarter of 2011, a former member of the intelligence forces witnessed the killing of five children in a secondary school during demonstrations.”

UN special representative Radhika Coomaraswamy told the BBC that in her experience she had never known a conflict where children were specifically targeted.

However, she also criticised the Free Syrian Army for putting children at risk by using them “in medical and service orientated jobs” on the front line.

Meanwhile, shelling on residential areas in Homs continued on Monday, according to the Activists News Association.

The group, which aims to support "citizen journalists" posted a video of the shelling on YouTube, which can be seen below - although there is no way of confirming its authenticity.