Russia on Tuesday denied bombing hospitals in northern Syria, with Kremlin spokesman Dmitry Peskov calling such accusations "unsubstantiated."

"Once again, we categorically reject and do not accept such statements," he said when asked whether Russian planes bombed hospitals in Syria, including one supported by Doctors Without Borders (MSF).

"Especially since every time, those who make such statements are unable to prove in any way their unsubstantiated accusations."

The Kremlin spokesman added that Moscow prefers to rely on "first-hand sources" of information, which he said in this case would be the Syrian government.

Syria's ambassador to Russia, Riad Haddad, on Monday accused the United States of bombing the MSF hospital and said that "Russian warplanes had nothing to do with any of it."

Strikes on hospitals in Idlib and Azaz killed almost 50 civilians including children, according to the United Nations, with UN Secretary General Ban Ki-moon saying the raids violated international law and undermined efforts to end the five-year conflict.

The MSF confirmed its hospital was hit, without assigning blame.

The Syrian Observatory for Human Rights, a British-based monitor, said it suspected that Russian warplanes were behind the attack, based on the location of the raids and the flight patterns and types of planes involved.

Turkish Prime Minister on Tuesday denounced "vile, cruel and barbaric planes" of the Russian airforce, saying they bomb "without discrimination between civilians and soldiers."

Russia's defence ministry however hit back with accusations that Turkey is shelling Syrian government forces from across the border.

"Since the end of last week Turkey is hitting Syrian government forces and patriotic opposition in border areas with large calibre artillery," spokesman Igor Konashenkov said in an emailed statement.

He accused Turkey of "hitting border villages in Aleppo province with artillery more than 100 times" and engaging in an "informational campaign against Russia to avoid losing control over north and northwest part of Syria."

Syria's government offensive, helped by Russian planes, has "freed from terrorists over 800 square kilometres of territory" with 73 towns and villages in Syria so far this month, including over 100 square kilometres in the past 24 hours in the north-west of the country, he said.

Russian planes hit 1593 "terrorist targets" in total in the past week, he added, without detailing exactly what was hit.

The Russian air force has carried out a campaign of strikes to help the ground offensive by the Syrian army since September.

The West accuses it of pursuing the goal of wiping out President Bashar al-Assad's moderate opposition rather than the stated objective to destroy jihadist groups like the Islamic State.