Children are being tortured and killed in Syria, where a conservative estimate has recorded 93,000 deaths since the conflict began, the UN says.

The organisation's human rights chief, Navi Pillay, said 7,055 minors had been killed, including at least 1,729 under the age of 10.

"Government forces are shelling and launching aerial attacks on urban areas day in and day out and are also using strategic missiles and cluster- and thermobaric bombs," she said.