Opposition forces now control the vast majority of Idlib after Al-Nusra Front and its allies in the Army of Conquest captured Ariha and surrounding villages yesterday in a swift assault.
It was the latest blow to loyalist forces who have been battling myriad groups of rebels for four years, after the fall of the ancient city of Palmyra to the Islamic State (IS) extremist group last week.
"The lightning offensive ended with a heavy pullout of regime forces and their allies Hezbollah from the western side of the city," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
The Army of Conquest -- Jaish al-Fatah in Arabic -- had also seized villages around Ariha as regime warplanes bombarded the city.
Also Read
Government forces had retreated from these areas to Ariha, which Abdel Rahman said was heavily defended by fighters from Iran and the Lebanese Shiite movement Hezbollah.
But the city fell to the Al-Nusra-led alliance "in a few hours," he said.
"Idlib is no longer part of these calculations, which explains the army's rapid retreat," he told AFP.
President Bashar al-Assad's regime still holds the Abu Duhur military airport and a sprinkling of villages and military posts in Idlib.