At least 224 people were killed in the first week of Ramadan in Syria, with the majority of the deaths resulting from bombings by Syrian and Russian warplanes, according to a monitor.

The Syrian Observatory for Human Rights, a Britain-based monitor, said on Monday that between 6 and 12 June - the first week of the Islamic holy month of fasting - at least 148 civilians, including 50 children and 15 women, were killed as helicopters dropped "explosive barrel" bombs.

It added that at least 12 people were killed in shelling by rebels and fighters from the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group. At least one man was executed by ISIL in the same period, the Observatory said.

"We ... renew our condemnation of the international community for its continued terrifying silence about the crimes committed against the Syrian people," the monitor said.

The death toll includes casualties from air strikes on a market in Idlib city, in which at least 40 civilians died on Sunday. Activists say most of those victims were women and children.

Several monitoring groups, as well as Turkish authorities, accused Russia of conducting the air strikes in Idlib, but Russian authorities denied any involvement.

The area is controlled by a coalition of rebel groups called The Army of Conquest, which includes al-Nusra Front. The coalition is not included in a partial ceasefire, which was negotiated in February.

The Observatory report comes as hundreds of civilians are fleeing the ISIL stronghold of Manbij in northern Syria and as fears grow for the thousands who remain trapped in the city, which is besieged by US-backed Kurdish and Arab forces.

The Syrian conflict, which began with peaceful protests in March 2011, has escalated into a multi-sided civil war.

The death toll has risen to more than 280,000 people, while half the country's population have been forced from their homes, according to UN estimates.