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.
The UN Security Council is to meet later on February 22 to discuss the situation.
UN Secretary-General Antonio Guterres has urged an immediate suspension of "all war activities" in the area, where he said people are living "in hell on earth," and German Chancellor Angela Merkel called for the European Union to step up pressure on Russia and Iran to end the violence in Syria.
"The [Syrian] regime is not fighting against terrorists, but against its own people, killing children, destroying hospitals, and this is a massacre to be condemned," Merkel told parliament on February 22.
Merkel also said that "Iran and Russia have a particular responsibility" as they are both supporting the government forces.
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.