DARAYA, Syria — Mass burials in this Damascus suburb on Sunday showed the carnage of the past few days in gruesome detail: scores of bodies lined up on top of one another in long, thin graves moist with mud.


In what is unfolding as one of the deadliest and most focused short-term assaults by the Syrian military since the uprising started nearly 18 months ago, witnesses and activist groups say hundreds have been killed in Daraya in the past week alone. Residents described how the Syrian Army first closed off the city, keeping civilians from fleeing, then methodically began a campaign of heavy shelling and house-to-house searches ending with executions.


A video of what activists described as the fifth and latest mass grave to be filled showed two small children near the edge. Up close, in the field where there were more bodies than people to wash and prepare them for burial, the scent of decay swirled and gunshot wounds could be seen in the heads of many men.


“The Assad forces killed them in cold blood,” said Abu Ahmad, 40, a resident of Daraya, where the Syrian government has waged a campaign it described as a “cleansing.” “I saw dozens of dead people, killed by the knives at the end of Kalashnikovs, or by gunfire. The regime finished off whole families, a father, mother and their children. They just killed them without any pretext.”


Even as many of the details are still difficult to verify or determine — the exact number killed, how many were executed or died from shelling — evidence of what activists described as a massacre continues to mount.


The death toll, rising all week, grew again on Sunday. A day after two activist networks, the Local Coordination Committees and the Syrian Observatory for Human Rights, said that more than 200 bodies had been found in the town, activists said another 15 bodies were discovered in the basement of a home in the area. That put the death toll for the week at more than 630 in the city, said the Local Coordination Committees, including nearly 300 people reported executed.


“Daraya, a city of dignity, has paid a heavy price for demanding freedom,” the group said in a statement, adding: “The death toll has doubled in the past few days due to field executions and revenge killings.”


Activists posted a video of what they said was the latest find. It showed a pile of bodies in the corner of a basement of what appeared to be a large home. Pools of blood darkened the gray concrete floor beneath a tangle of bodies. Several others — including a man with what clearly appeared to be a gunshot wound to the head — were splayed out behind nearby walls.


Two other videos posted Saturday showed corpses lined up as well, with activists declaring that the largest discovery occurred late Saturday night in the basement of a mosque. The Local Coordination Committees said about 150 bodies had been discovered there. Most were men killed in executions, activists said, though they also noted that among the dead found all over the city, there were also several women and children.


At the grave site, the bodies of a few children could be seen, but it was unclear whether women were buried there, as well.


Daraya, a city of several hundred thousand, has been reported as a mainstay of opposition support within the capital area since the start of the uprising. Its location is also critical: it abuts the Mezze military airport, a major base for Syrian forces. There are farms on the fringe of town, and small furniture factories dominate the city center.


When the government assault started, activists said that rebels had established a large armory inside the city. They said it had been rumored to hold missiles, a detail that could not be confirmed, perhaps to target helicopters at the Mezze airport.


The government operation began early last week. Troops first surrounded Daraya and set up checkpoints, blocking food and other supplies from entering, residents said. Electricity was cut, then Internet and phone service.