Beirut (AFP) - Russian air strikes in Syria have killed 370 people since they began on September 30, around a third of them civilians, a monitoring group said Tuesday.

The Syrian Observatory for Human Rights said 243 rebel fighters had been killed, among them 52 from the Islamic State group, along with 127 civilians.

Among the civilians were 36 children and 34 women, according to Observatory director Rami Abdel Rahman.

Moscow began air strikes in Syria last month in cooperation with the government in Damascus and says it is targeting the Islamic State group and other "terrorists".

But Syrian rebels and their backers accuse Russia of targeting moderate and Islamist rebels in a bid to bolster the regime.

Moscow's strikes have hit multiple provinces across the country, including strongholds of IS like Raqa province.

But they have focused most heavily on several provinces where Syrian regime forces are leading offensives against an array of opposition forces that do not include IS.