Assad's forces have preferred to use air power and artillery to hit areas where rebels are positioned and infantry raids normally occur only once many have fled. Activists said they feared for civilian inhabitants in the latest offensive.
Syrian activist Abu Yasser al-Shami said that his friends living in Yarmouk, a densely populated Palestinian refugee camp where 10 people were killed on Friday in shelling, had fled the area on Saturday morning after government troops swept in.
"Assad's forces stormed al-Basel hospital in Yarmouk Camp and arrested many of the injured civilians," he said over Skype.
When insurgents thrust into central parts of the capital in July, they were swiftly pushed back to southern districts, like Yarmouk, where there is a thinner state security presence.
But residents complain that the army uses indiscriminate artillery and air strikes. Palestinians have been divided over whether or not to support Assad, but there are signs that more and more are now starting to back the uprising.
The Syrian Observatory for Human Rights, an opposition watchdog based in London, said shells rained down on Hajar al-Aswad district, which neighbors Yarmouk, on Saturday.
It said 170 people were killed in bloodshed on Friday across the country, many of them in Damascus and northern Aleppo, where rebels say they control more than half of what is Syria's most populous city and commercial center.
The Observatory says more than 23,000 people have died in an uprising that has lasted more than 17 months. Around 200,000 Syrians have fled to neighboring Turkey, Jordan and Iraq.
The conflict is spilling over Syrian borders and has raised sectarian tension in the region given that the revolt has been led by majority Sunni Muslims against a president who is Alawite, an offshoot of Shiite Islam.
Assad's use of military force to quell the uprising has cost him many allies in the Arab and Muslim world and caused a trickle of defections from Syrian government and army ranks.
Two Syrian diplomats in Malaysia announced late on Friday that they had joined the opposition, according to a report by pan-Arab television channel Al Arabiya.
Two men identifying themselves as First Secretary Imad Ahmar and Attaché Mahmoud Obedi from Syria's Kuala Lumpur embassy read out a statement on the channel declaring their "support for the Syrian people's revolution against the tyrannical regime."
But the defections so far are seen largely as symbolic and Assad has increasingly relied on a close circle of relatives and senior members of his minority Alawite sect dominating the ruling elite to maintain his grip on power.
BEIRUT (Reuters) -- Syrian troops stormed into a Palestinian refugee camp in Damascus, opposition activists said, after a four-day artillery assault on the southern suburb where rebels fighting to oust President Bashar Assad have dug in.