Al-Qaeda-affiliated militants and other Syrian rebel groups have attacked the government-held city of Idlib, briefly seizing several official buildings.
The Nusra Front said its fighters killed dozens of government soldiers before being pushed back.
The Syrian government has maintained control of Idlib city in the country's north-west since it was briefly taken over by rebel groups in 2012.
Syria's civil war, in its fourth year, has claimed more than 200,000 lives.