Air strikes pounded a jihadist-held area near Damascus on Sunday, footage broadcast by Syrian state TV stations showed, as the Syrian government stepped up efforts to wipe out the insurgency's last foothold near the capital.

Thick clouds of smoke rose from the al-Hajar al-Aswad area and the sound of jets could be heard in broadcasts from the area just south of Damascus that is controlled by insurgents from the Islamic State and Nusra Front groups.

UNRWA, the UN agency that cares for Palestinians, said two Palestinian refugee civilians - a father and son - had been killed in their home in the adjacent Palestinian camp of Yarmouk.