A pro-regime Palestinian paramilitary group mourned three officers they said had been killed by a former Al-Qaeda group, as the regime stepped up efforts to wipe out the insurgency's last foothold south of the capital.
The Fateh al-Intifada militia has engaged in fierce clashes with Hay'at Tahrir al-Sham and the Islamic State (ISIS) group in the Palestinian refugee camp of Yarmouk and the Al-Hajar al-Aswad district.
Hay'at Tahrir al-Sham said it had killed more than 20 Palestinian fighters loyal to Syrian President Bashar al-Assad since the clashes erupted four days ago.
On Sunday, regime warplanes carried out fresh airstrikes on the southern neighborhoods of Damascus. Local activists said more than 200 raids were conducted since Thursday.
Thick clouds of smoke rose from Al-Hajar al-Aswad, as the sound of jets could be heard overhead in live broadcasts from the area.
The area is part of an enclave just south of Damascus that includes Yarmouk camp and is controlled by militant insurgents from ISIS and Hay'at Tahrir al-Sham, formerly known as the Nusra Front.
It is adjoined by a pocket held by other rebel groups fighting under the Free Syrian Army banner.
Assad, backed by Iran and Russia, is seeking to crush the last few besieged rebel enclaves, building on the defeat of insurgents in the Eastern Ghouta region, which was the rebels' last major stronghold near the capital.
Rebel fighters on Saturday began to withdraw from an enclave they held northeast of Damascus in the Eastern Qalamoun region in a surrender agreement with the government. They are being transported to opposition-held territory on the Turkish border.
Although the conquest of Eastern Qalamoun and the enclave south of Damascus will leave just one remaining besieged rebel enclave, north of the city of Homs, large parts of Syria at the borders with Jordan, Israel, Turkey and Iraq remain outside Assad's control.
Anti-Assad rebels hold a chunk of territory in the southwest and the northwest, and Kurdish-led militias, backed by the United States, control an expanse of northern and eastern Syria. (With agencies)
This article was edited by The Syrian Observer. Responsibility for the information and views set out in this article lies entirely with the author.