At least 39 civilians were killed Tuesday in suspected Russian air strikes on two markets in northern Syria, a monitoring group said.

The raids killed 16 civilians at a market for fuel in Maarat al-Naasan, a village in Idlib province, according to the Syrian Observatory for Human Rights.

Another 23 civilians, including five women, were killed after strikes on a village held by the Islamic State group in the northern Aleppo province.

Observatory head Rami Abdel Rahman told AFP four IS jihadists were also killed in those raids on the village of Maskana, which hit a market as well.

Both tolls were likely to rise as many people were critically wounded, the Britain-based monitor said.

The Observatory relies on a network of sources on the ground to collect its information, and identifies aircraft based on their flight patterns and munitions used.

Russia began its air war in Syria on September 30, conducting air strikes against a range of anti-regime armed groups including US-backed rebels and jihadist groups.

Moscow has said it is fighting and other "terrorist groups," but its campaign has come under fire by Western officials who accuse the Kremlin of seeking to prop up Syrian President Bashar al-Assad.

IS has swept across eastern parts of Aleppo province from its bastion in Raqa, fighting both non-jihadist rebels and regime troops along the way.

But the northwestern province of Idlib is controlled by the fiercely anti-IS Army of Conquest alliance, led by jihadist rival Al-Qaeda affiliate Al-Nusra Front.

More than 250,000 people have died since Syria's conflict erupted in March 2011, and millions have fled their homes in the war-torn country.