The latest strikes hit several towns in Eastern Ghouta, a semi-rural area which lies just east of the capital Damascus and has been controlled by Islamist and jihadist groups since 2012.

Three children were among those killed in Wednesday's strikes, which also left at least 200 wounded, according to the Syrian Observatory for Human Rights.

The latest casualties brought to 274 the number of civilians killed since Sunday and to at least 1,400 the number of those wounded in the deadliest wave of strikes to date on Eastern Ghouta.

Rami Abdel Rahman, the head of the Britain-based observatory, said at least 67 children were among those killed this week.

The regime of President Bashar al-Assad has been massing forces around the enclave this month, raising fears that an even deadlier ground assault could be launched imminently.

The area has been besieged since 2013 and the humanitarian situation inside the enclave is dire.

Aid groups have said their assistance can no longer reach those in need due to the heavy bombardment and have warned of an unfolding catastrophe.