The Syrian army advanced toward the Turkish border on Monday in a major offensive backed by Russia and Iran that rebels say now threatens the future of their nearly five-year-old insurrection against President Bashar al-Assad.
Iranian backed-militias played a key role on the ground as Russian jets intensified what rebels call a scorched earth policy that has allowed the military back into the strategic northern area for the first time in more than two years.
"Our whole existence is now threatened, not just losing more ground," said Abdul Rahim al-Najdawi from Liwa al-Tawheed, an insurgent group.
"They are advancing and we are pulling back because in the face of such heavy aerial bombing we must minimize our losses."
The Syrian military and its allies were almost five km (3 miles) from the rebel-held town of Tal Rafaat, which has brought them to around 25 km (16 miles) from the Turkish border, the rebels, a residents and a conflict monitor said.
The assault around the city of Aleppo in northern Syria has prompted tens of thousands to flee toward Turkey, which is already sheltering more than 2.5 million Syrians, the world's largest refugee population.
In the last two days escalating Russian bombardment of towns north west of Aleppo, Anadan and Haritan, brought several thousand more, according to a resident in the town of Azaz.