Ten children were among 24 people killed in strikes on a rebel enclave near the Syrian capital, as the UN’s humanitarian chief paid his first visit to the country.

The Syrian observatory for human rights said, either regime or Russian aircraft were responsible for the raids, the most deadly of which killed 13 civilians including seven children in the Hammuriyeh district of eastern Ghouta.

Rebels bombarded two districts of the capital in retaliation, with Syrian state media reporting four people were killed.

Eastern Ghouta has been under government siege since 2013 and its estimated 400,000 inhabitants are suffering severe shortages of food and medicine.

The observatory said the deadliest strikes hit the Hammuriyeh district, while more than 80 people were wounded in the bombardments of the rebel territory.

The latest bloodshed in Syria’s war which is estimated to have claimed the lives of 340,000 people since 2011 came as UN humanitarian boss mark Lowcock discussed getting aid to civilians.

The United Nations has said some 500 people are in critical condition inside eastern Ghouta and need to be evacuated for urgent medical treatment.

Twenty-nine patients, mainly children, were allowed out in December under a deal struck between the regime and rebels.