Warplanes and artillery bombarded eastern Ghouta -- a rebel enclave near Syria's capital, Damascus -- for a fifth straight day on February 22, as the United Nations pleaded for a halt to one of the fiercest air assaults of the seven-year civil war.
The UN's humanitarian coordinator for Syria, Panos Moumtzis, said that at least 370 people have been killed and 1,500 injured since the Syrian government and its allies escalated their offensive on the region on February 18.
In New York, the UN Security Council met to discuss a draft resolution calling for a 30-day nationwide cease-fire.
Russia's UN Ambassador Vassily Nebenzia told the meeting that there was no agreement on the draft text, sponsored by Sweden and Kuwait, and that he had proposed amendments.
The developments come amid a growing outcry from Western capitals, the United Nations, and humanitarian groups over what UN relief chief Mark Lowcock called an "entirely known, predictable, and preventable humanitarian disaster unfolding before our eyes."
U.S. State Department spokeswoman Heather Nauert said that Russia "bears unique responsibility" for what she called "the devastation and the deaths" in Syria.
Earlier, German Chancellor Angela Merkel told her country's parliament that Iran and Russia had "a particular responsibility" as they are both supporting Syria's government forces which she said are "not fighting against terrorists, but against its own people."
However, Kremlin spokesman Dmitry Peskov denied that Russia has any responsibility for the situation in eastern Ghouta, saying, "Those who support the terrorists are responsible."
Russian news reports, meanwhile, said Moscow has sent more warplanes to Syria, including its latest Su-57 fighter jets.
Russia and Iran have given Assad's government crucial support throughout the seven-year-old war in Syria, which began with a government crackdown on protests in 2011.
Moscow helped turn the tide of the conflict in Assad's favor by a launching a campaign of air strikes in 2015 and stepping up its military presence on the ground.
With reporting by Reuters, AP, and the BBC