Government forces are on the brink of seizing the last part of southwestern Syria in insurgent hands, the Syrian Observatory for Human Rights said on Monday.
Advancing government forces have seized all but three villages held by the Islamic State-affiliated faction, the Khalid Ibn al-Walid army, that controlled the Yarmouk Basin, the war monitor said.
Earlier in July, the Syrian regime and its allies, backed by Russian air strikes, widened their offensive on the southwest to include the region which borders the Israeli-occupied Golan Heights and Jordan.
"Khalid Ibn al-Walid army now controls three small villages, which constitute less than one percent of the area it once controlled in Yarmouk Basin," Rami Abdelrahman, director of the Britain-based war monitor, told Reuters by phone.
President Bashar al-Assad is seeking to recover the entire southwestern corner of Syria in an offensive that began last month and has so far recovered swathes of territory from rebels fighting under the Free Syrian Army (FSA) banner.
Assad is already in his strongest position since the early days of a seven-year civil war that has killed half a million people. A successful assault on the southwest would leave insurgents seeking to overthrow Assad largely confined to a single pocket of territory in the northwest of the country.
Assad has so far recovered swathes of Deraa province in the southwest from FSA rebels, many of whom have been forced into surrender agreements mediated by Russian officers. The United States, which once armed the southern FSA rebels, told them at the start of the attack not to expect its intervention.