But government forces ramped up military pressure on Eastern Ghouta starting Sunday, sending more than 260 rockets sailing onto opposition-controlled towns there.
The UN on Monday had demanded an end to the targeting of civilians in Syria.
Eastern Ghouta, the last remaining rebel-held area near Damascus, has been under siege by government forces since 2013.
The European Union's foreign policy chief Federica Mogherini and European Commissioner for Humanitarian Aid and Crisis Management Christos Stylianides also issued a joint written statement late Monday regarding the humanitarian situation in Eastern Ghouta and Idlib.
McDonald said more than 100 children in Eastern Ghouta need evacuation for life-saving medical treatment that is not available for conditions including cancer and kidney disease.
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"Ghouta is now living in a state of terror because of the bad shelling".
Traumatised innocence: Syrian children cry at a makeshift hospital in Douma following air strikes on Mesraba in the besieged Eastern Ghouta region near Damascus, on February 19th, 2018.
"We don't have the words anymore to describe our outrage at what is happening to children inside Syria", she said by phone from Amman, the capital of neighbouring Jordan. "We are running out of anaesthetics and other essential medications", he said.
Moscow did not comment on the renewed bombing in eastern Ghouta on Tuesday.
The attacks "deliberately target inhabited areas and civilian infrastructure, including medical ones".
"We will continue appealing for access to all those in need, and remind those responsible of their obligation to grant it under the worldwide humanitarian law", Zatari said.
There are nearly 400,000 people in Eastern Ghouta, the largest opposition stronghold left near the capital, according to the UN.