Russia has strongly rejected accusations by Turkey that it has committed war crimes in Syria.
The Turkish foreign ministry has blamed Russia for missile attacks on several hospitals and schools in northern Syria on Monday that killed up to 50 people.
An image released by Medecins Sans Frontieres (MSF) of a hospital hit by air strikes. Photo: AFP / HO / MSF
Kremlin spokesman Dmitry Peskov said "those who make such statements are not capable of backing them up with proof".
Russia has been accused, by Turkey among others, of being responsible for the attacks on rebel-held areas.
The UN said "intentionally directing attacks" at hospitals and medical units would constitute a war crime.
Monday's strikes hit two hospitals - including one for mothers and babies - and a school sheltering internally displaced people in Azaz, near the border with Turkey, the UN said. Thirty-four people were killed and dozens wounded.
Two hospitals were also struck in Maarat al-Numan, further south in Idlib province, killing at least 12 people and wounding about 36.
One of the hospitals in Maarat al-Numan was supported by Medecins Sans Frontieres (MSF). It was reportedly struck by four missiles in what MSF said was "direct targeting" over the course of 90 minutes.
MSF said 11 people died, including five patients, and that the toll was likely to rise.
Mego Terzian, president of MSF France, told Reuters "either the [Syrian] government or Russia" was responsible.
But Mr Peskov told the BBC that the only proof Russia would accept from the ground "comes from the Syrian authorities". He said their evidence "shows the opposite".
The Syrian ambassador to Moscow, Riad Haddad, previously said the US was to blame, a claim the Pentagon dismissed as "patently false".
The strikes came days after world powers - including Russia - agreed to work towards a selective truce in Syria, due to begin later this week.
Earlier, Syrian President Bashar al-Assad, in his first comments on Friday's "cessation of hostilities" plan, said it was doubtful all parties would be putting down their weapons within a week.
- BBC