Report into children and armed conflict says children have been tortured and used as human shields by forces loyal to Assad

Syrian government forces and militia loyal to the Assad regime are killing and sexually abusing children and using them as human shields, the UN says, amid fears that the conflict is intensifying.

Kofi Annan said he was "gravely concerned" about the escalation of fighting in Syria, citing the shelling of opposition areas in central Homs province and reports of mortar, helicopter and tank attacks in the town of Haffa and its surrounding villages in Latakia province on the Mediterranean coast. The US state department spokeswoman Victoria Nuland voiced fears about reports that the regime "may be organising another massacre" in Latakia, where UN monitors have been impeded.

The UN secretary general Ban Ki-moon's annual report on children and armed conflict during 2011 included Syrian government forces and the allied shabiha for the first time on a list of 52 governments and armed groups that recruit, kill or sexually attack children in armed conflicts.

"In almost all recorded cases, children were among the victims of military operations by government forces, including the Syrian armed forces, the intelligence forces and the shabiha militia, in their ongoing conflict with the opposition, including the Free Syrian Army," the report says.

The report quotes a witness to an attack on the village of Ayn l'Arouz in Idlib province on 9 March 2012 in which several dozen boys and girls between the ages of eight and 13 were forcibly taken from their homes and "used by soldiers and militia members as human shields, placing them in front of the windows of buses carrying military personnel into the raid on the village". The UN said it had collected dozens of witness accounts from children as young as 14 who were tortured in detention, as well as from former members of the Syrian military who were forced to witness or carry out acts of torture, the report says.

Most child victims of torture described being beaten, blindfolded, subjected to stress positions, whipped with heavy electrical cables, scarred by cigarette burns and in one case subjected to electrical shock to the genitals, the report says. One witness reported seeing a boy about 15 years old die as a result of repeated beatings.

The UN's special representative for children and armed conflict, Radhika Coomaraswamy, told the BBC: "We are really quite shocked. Killing and maiming of children in crossfire is something we come across in many conflicts but this torture of children in detention, children as young as 10, is something quite extraordinary, which we don't really see in other places."

She also criticised the rebel Free Syrian Army for endangering children by placing them on the frontline, albeit mainly in mainly in medical and service orientated jobs.

More bloodshed was reported early on Tuesday. The Local Co-ordination Committees activist group said 11 people had been killed when government troops shelled a protest in the eastern province of Deir Ezzor, bordering Iraq, after more than 100 people were killed on Monday. The British-based Syrian Observatory of Human Rights put Monday's death toll at 82, with clashes between military forces and rebel fighters in Homs, Idlib and Latakia provinces. Syrian activists say 13,000 people have been killed since the uprising began in March 2011. Restrictions on access to foreign media make the death tolls impossible to verify.

The US and UK have refused to rule out military intervention but appear wary of entering another conflict as they attempt to exit Iraq and Afghanistan. Russia and China have constantly warned against foreign interference and have already vetoed two UN security council resolutions that threatened sanctions against the Assad regime.