At least 18 pro-Syrian regime combatants have been killed in 24 hours of fighting in southern Damascus against the Islamic State group, a monitor said Tuesday.
That brought to at least 52 the number of pro-government fighters killed in nearly a week of military operations against Yarmuk and adjacent IS-held neighbourhoods, the Syrian Observatory for Human Rights said.
No confirmation of the casualties was available from Syrian officials, who do not usually disclose losses within army ranks.
The Britain-based Observatory said at least 35 jihadist fighters were also killed over the same period.
There are an estimated 1,000 IS fighters left inside the enclave in the capital's southern neighbourhoods, which includes Yarmuk and the adjacent districts of Hajar al-Aswad and Qadam.
From their perch in Yarmuk -- which has a view of the presidential palace in Damascus -- jihadists have fired rockets on the capital's centre.
According to state news agency SANA, five civilians were killed Tuesday when a mortar shell crashed into a market area.
The Observatory said the fighting on the ground was fierce, as IS attempted a desperate defence of one of its very last bastions in the country.
The Syrian army's focus on Yarmuk, once the country's largest Palestinian refugee camp, comes as part of its campaign to secure the capital.
It recently retook the opposition enclave of Eastern Ghouta, then reached a string of deals last week for the transfer to northern Syria of rebels who had been allowed to remain in villages near Damascus as part of 2016 reconciliation agreements.
A successful operation in Yarmuk, which is anticipated, would seal the regime's reconquest of the capital, a major prize for a resurgent President Bashar al-Assad.