Beirut (AFP) - Suspected Russian air strikes have killed 46 civilians, mostly women and children, in northern Syria, the Syrian Observatory for Human Rights said on Friday.

Observatory head Rami Abdel Rahman said warplanes had bombarded Raqa, the Islamic State group's de facto Syrian capital, as well as the towns of Azaz and Al-Bab in Aleppo province, on Thursday.

Six children and 11 women were among the dead, and dozens of people were wounded, the Britain-based monitor said.

The toll in Raqa also included two rescue workers, according to Abdel Rahman, but he said no suspected militants were killed in the three areas hit.

In the northwestern Idlib province, air raids on Jisr al-Shughur town "probably by Russian planes" killed at least 14 people -- seven children and seven women -- according to Abdel Rahman.

The town is controlled by Islamist rebels.

Russia has been conducting an intense air war on armed opposition groups throughout Syria for nearly three months.

It has been criticised by the West and by rebels for targeting non-jihadist groups and incurring civilian casualties.

The Observatory says it distinguishes between strikes carried out by Syrian, Russian and US-led coalition aircraft based on flight patterns indicating whether planes took off from inside the country, as well as the type of planes and ordnance used.

It identifies those killed through its network of activists, hospital personnel and fighters on the ground.

According to Abdel Rahman, Russian strikes since September 30 have left around 1,900 people dead, including more than 600 civilians. The toll includes 526 IS jihadists and 739 other rebels.

More than 250,000 people have been killed in total since Syria's conflict erupted in 2011.