At least two people have been killed and several, including babies, were injured in an air strike on a maternity hospital in Syria's Idlib province.
Deputy Defense Minister Anatoly Antonov was quoted by the Interfax news agency as saying Friday that Russian Federation is "ready for close and constructive cooperation with all global humanitarian organizations and, of course, with the office of the United Nations special envoy on Syria".
The charity also published a 15-second long video footage from the hospital in the immediate aftermath of the attack on Friday.
Elsewhere, the Observatory said IS militants had recaptured the nearby village of al-Bouweir and killed 24 civilians.
The Syrian Observatory for Human Rights said a militant from the Al-Nusra Front, which has changed its name to Jabhat Fateh al-Sham, was killed in the raid.
Russian authorities have promised to open three routes to allow unarmed rebels and civilians to flee after coming under increasing worldwide pressure, but the pledge was met with distrust.
The hospital, which was set up in June 2014, delivered about 340 babies in June, the spokeswoman said.
"How can you expect people to want to walk through a corridor, thousands of them, while there is shelling, bombing fighting?" Mr de Mistura said.
He reiterated that civilians who left should do so only through their own choice.
Amnesty International said the strike "appears to be part of a despicable pattern of unlawful attacks deliberately targeting medical facilities" across Syria and a "potential war crime". "Casualties have been reported and we are awaiting confirmation of numbers", the statement said. The town is encircled by the Kurdish-led Syrian Democratic Forces.