Meanwhile two Israeli missiles hit near Damascus airport overnight, SANA and the Syrian Observatory for Human Rights war monitor said. SANA said the missile strikes near Damascus international airport were a sign of support by Israel for the terrorists in the southwest, Reuters reported.
The observatory said the overnight Israeli strikes targeted warehouses belonging to non-Syrian militias loyal to the Syrian government.
Syria's southwest region is strategically sensitive because of its proximity to Jordan and the Israeli-occupied Golan Heights. The United States and Russia last year agreed a "de-escalation" zone in the area that has helped to contain the violence there.
SANA and media outlets run by Damascus ally Hezbollah said the Syrian Army had taken control of the town of Busra al-Harir, the nearby Laja area and was now advancing further south.
The capture of the area cut across a terrorist-held finger of territory in northeastern Dara’a Province, where government forces have pressed their assault despite US warnings.
The United States has told Syrian terror factions they should not expect military support to help resist the offensive.
The United States has repeatedly warned Assad against violating the de-escalation zone, saying it would have serious repercussions and pledging "firm and appropriate measures."
There was no statement from terror groups about the government advances.
At least 45,000 people have fled the fighting in the southwest, heading toward the border with Jordan, the United Nations said on Tuesday.
"We expect the number of displaced people could more than double as violence escalates," Bettina Luescher, spokeswoman for the UN's World Food Programme (WFP), said.
WFP had provided food to 30,000 people and plans to deliver more in the coming days over the border from Jordan, she said.