Syrian government forces are closing in on the last part of Damascus which is not yet in their control; the area is mainly held by ISIS fighters.
Having captured the town of Dumayr northeast of the Syrian capital, the enclave of Yarmouk came under intense bombardment.
ITV News correspondent Dan Rivers, reporting from Damascus, said late Thursday: "We've been watching for several hours this afternoon and this evening this intense artillery barrage and airstrikes pummeling this area."
Yarmouk had been the site of large Palestinian refugee camp, but the area is now largely occupied by fighters with the so-called Islamic State, or ISIS, and other armed group, although a small number of refugees remain.
"Negotiations have been going on to try to give safe passage to those ISIS fighters to desert areas, but those clearly broke down and the army has gone in and gone in very heavy," Rivers said.
Syrian forces took over Dumayr on Thursday. Footage on the state-affiliated al-Ikhbariya TV station showed residents of the town welcoming the security forces.
The Syrian army has focused its effort on recapturing Damascus having retaken the eastern Ghouta, the site of a chemical weapons attack.
UN inspectors have remained unable to access the site, having been fired on by unidentified gunmen on Wednesday.