Syrian regime air strikes have killed six civilians in southern Damascus where government forces are battling the ISIS terrorist group, a war monitor said Wednesday. The six, including two men and their wives, were killed in the strikes on the Palestinian camp of Yarmuk late Tuesday, the Syrian Observatory for Human Rights monitoring group said. Regime strikes and rocket fire Wednesday morning targeted the neighboring districts of Hajar al-Aswad and Qadam, the Britain-based monitor said. In Qadam on Tuesday, soldiers could be seen pushing a fresh advance, backed by Syrian regime air strikes and artillery fire, during an organized press tour. Columns of black smoke were snaking up from a monochrome sea of devastated buildings, AFP reported. The salvos of shelling paused briefly, and the steady crack of machinegun fire took their place. Barricades sealed off every street in Qadam, which was once a bustling stop on Syrias train line but whose carriages are now abandoned and left in ruins. From their perch in Yarmuk -- which has a view of the presidential palace in Damascus -- jihadists have fired rockets on the capitals center. The latest civilian deaths bring to 18 the total of non-fighters killed in regime bombardment on the capitals southern neighborhoods since Thursday last week. Yarmuk, which is now ISISs last urban redoubt in Syria or Iraq, was once Syrias biggest Palestinian refugee camp, home to around 160,000 people. But the United Nations agency for Palestinian refugees UNRWA says most of the 6,000 refugees still living in the camp last week have since fled. At least 52 pro-regime fighters have been killed in fighting to expel ISIS from the capitals southern suburbs since April 19, the Observatory says. Syrian officials do not usually disclose losses within army ranks. The monitor has said at least 35 jihadist fighters were also killed during the same period. There are an estimated 1,000 ISIS fighters left inside Yarmuk and the adjacent districts of Hajar al-Aswad and Qadam. ISIS swept across large parts of Syria and neighboring Iraq in 2014, declaring a cross-border "caliphate" in areas the jihadists seized. At its height, their pseudo-state covered an area the size of Italy, but ISIS has since lost most of the land it controlled in both countries. More than 350,000 people have been killed since Syrias war started in 2011 with the brutal repression of anti-regime protests.