At least 38 more civilians were killed by Bashar al-Assad regime forces in besieged Eastern Ghouta region on Sunday, Syrian Civil Defense sources said.
The regime's ground and air attacks continued on civilians in the opposition-hold area near capital Damascus despite decisions to implement a ceasefire made separately by Russia and the UN Security Council.
The sources from the Syrian Civil Defense, also known as the White Helmets, said 31 civilians were killed in Duma district in airstrikes and missile attacks.
Seven people were also killed when Assad regime forces attack a residential area between Misraba and Duma districts with rocket and mortar shells.
Late Saturday, regime forces and its supporters have advanced into the opposition-held areas, capturing the town of al-Nashabiya, and the villages of Otaya, Hazrama.
The death toll in the region may rise as the attacks are still ongoing. The number of casualties in Eastern Ghouta since Feb. 19 has reached 756.
Last Saturday, the UN Security Council adopted a resolution calling for a 30-day ceasefire in Syria without delay.
In an unusually lengthy statement, the U.S. strongly condemned the regime and its primary international supporter: Russia for violating the ceasefire, saying Moscow "has gone on to ignore its terms and to kill innocent civilians under the false auspices of counterterrorism operations".
"This is the same combination of lies and indiscriminate force that Russia and the Syrian regime used to isolate and destroy Aleppo in 2016, where thousands of civilians were killed," White House spokeswoman Sarah Huckabee Sanders said.
Russian military aircraft conducted some 20 daily sorties on Damascus and Eastern Ghouta between Feb. 24-28 from the Russian-operated Humaymim Airfield to the northwest, the White House said.
"The Assad regime, along with its backers in Moscow and Tehran, should adhere to UNSCR 2401, cease hostilities in and around Eastern Ghouta, and allow unfettered delivery of humanitarian aid to the nearly 400,000 innocent civilians in critical need," Sanders added.
Eastern Ghouta, a Damascus suburb, has been under siege for the last five years and humanitarian access to the area, which is home to some 400,000 people, has been completely cut off.
In the past eight months, forces of the Assad regime have intensified their siege of Eastern Ghouta, making it nearly impossible for food or medicine to get into the district and leaving thousands of patients in need of treatment.