A coalition of insurgent groups seized the last city in the northwestern province of Idlib still held by the government.
The coalition, called Jaish al-Fatah or the Conquest Army, said it had taken over Ariha, near the Turkish border, and overrun several checkpoints that defended the city on May 28.
Syria's Al-Qaeda offshoot, Jabhat al-Nusra, is a major part of the coalition.
After heavy clashes with the militants, the army admitted its forces had pulled back from the city, the latest in a string of defeats for President Bashar al-Assad's forces.
"Jaish al-Fatah has taken full control of the city of Ariha after a lightning offensive," Syrian Observatory for Human Rights chief Rami Abdel Rahman said.
"There are many bodies that litter the streets," said a rebel source, adding that the insurgents were searching for Assad's forces inside the city.