A surprise "Islamic State of Iraq and Syria" (ISIS) group attack on a Syrian regime position killed more than two dozen pro-government forces in the country's vast desert, AFP reported Tuesday (May 22nd).

"At least 26 regime soldiers and allied forces were killed in an ISIS attack at dawn today, against one of their posts in the Syrian Badiya," said the Syrian Observatory for Human Rights.

Syrian police deployed across southern Damascus on Tuesday, a day after regime forces captured remaining areas from ISIS.

The regime on Monday seized Yarmouk Palestinian refugee camp, Tadamun and al-Hajar al-Aswad, putting Damascus fully under its control for the first time since 2012.

The UN Palestine refugee agency (UNRWA) said it was almost impossible to imagine people returning to Yarmouk, which has suffered heavy damage.

"Yarmouk was once the thriving home of 160,000 Palestinians. Today it lies in ruins, with hardly a house untouched by the conflict," spokesman Chris Gunness said.

"The public health system, water, electricity, basic services for life are severely damaged. The debris of this pitiless conflict is everywhere," he said. "In that environment, it is hard to see how people can go back."

Up to 200 civilians are still in Yarmouk, he said, including those too old or sick to flee.

"The situation they face is inhumane by any standards and we need humanitarian access urgently," he said, noting that UNRWA has not had access to Yarmouk since 2015.