Syrian security forces surrounded and raided a rebellious southern district in Damascus, arresting more than 100 people on Thursday, state television said, and opposition activists said several others were shot dead.

The campaign is the latest step in an effort by state forces to stamp out a presence in the Syrian capital of insurgents who are fighting to topple President Bashar al-Assad.

An activist in the Yarmouk district, where rebels have been hiding out in recent days, said tanks and soldiers had sealed all the entrances. Hundreds of soldiers were searching the area on foot and on trucks mounted with heavy machineguns.

"We are trapped here. Only children and older men or women can leave. Young men, who could be rebels or activists, and even young women, who could also be activists, are stuck inside," an activist called Abu Salam told Reuters on Skype.

"We are hiding in our homes. I am afraid to leave the house so I am sitting here waiting to see if they reach my street, if I will be arrested or shot dead," he said.

Yarmouk is an unofficial camp for Palestinian refugees. The densely populated, impoverished district in southern Damascus is packed with concrete buildings.

This summer, many districts of southern Damascus became a daily battleground in an 18-month-old popular revolt against Assad that has escalated into civil war.

Assad's supporters say they are not facing homegrown opposition but rather militants funded from abroad.

Syrian state television said 100 people had been arrested in Yarmouk, and said its forces searching another nearby district were "raiding terrorists dens" and had killed several people inside them.

In Yarmouk, the activist Abu Salam said at least three people, two men and a young woman, were shot dead when soldiers saw them running out of a park on Thursday morning. Another five rebels found hiding out in the area were executed, he said.

A resident who toured Yarmouk a day earlier said rebel fighters, who have been flushed out of many surrounding districts, had pulled into a southern section of the district and come under intense army bombardment overnight.

Activists and witnesses who spoke to Reuters say that many parts of the districts in Damascus's southern outskirts, where insurgents have been trying to maintain a foothold, have been reduced to rubble.

They said entire buildings had collapsed and the stench of decaying bodies filled the streets. "We are too afraid to go get them because security forces are there and will ask why we are coming for these people," said Abu Salam. – Reuters