At least 70 people were killed and 550 wounded in attacks on a marketplace in a rebel-held area east of the Syrian capital Damascus, Doctors Without Borders (MSF) said Saturday. The Syrian Observatory for Human Rights had announced a death toll of at least 59, including five children, in Friday's attacks on Douma. Douma is in Eastern Ghouta, the largest opposition stronghold in Damascus province. "This was an extremely violent bombing," said the director of a nearby MSF-supported hospital who assisted in the first wave of mass-casualty response. "The wounds were worse than anything we've seen before." "We had to do many amputations," he said. "We did our best to cope, but the number of critically wounded was far beyond what we could handle with our limited means." The nearest makeshift hospital had been bombed on Thursday, killing 15 people, so medical workers struggled to cope with the influx of injured, MSF said. "The devastation caused by the initial air strike on the market was exacerbated by further shelling on the rescue teams who were attending to the wounded," it added. The bombardments came as air raids by Syrian government forces and Russian warplanes intensified across the country. Moscow's month-old military intervention in support of President Bashar Assad has alarmed the United States and its allies, as world powers step up diplomatic efforts to end the war. Syrian government forces fired missiles into a marketplace in the town of Douma northeast of Damascus on Friday in the bloodiest attack on the area for weeks, the Syrian Observatory for Human Rights said. Also Friday, 32 civilians, among them 12 children, were killed in airstrikes on opposition-held areas of Syria's second city Aleppo, the Observatory said. "MSF fears the intensification of bombing that has been seen in northern and central Syria over the course of October could become even more horrific if it spreads to besieged areas around Damascus, where almost a million people are trapped," it said in a statement. On Saturday, at least 15 airstrikes hit the area, the Observatory said. Syria's four-year-old conflict has killed an estimated 250,000 people and driven more than 11 million from their homes.