A human rights group says at least 18 people were killed and many more, including civilians were injured, in an explosion in Idlib on Sunday.
The Syrian Observatory for Human Rights said the explosion targeted the headquarters of a minor rebel faction in the northwestern city.
And, videos uploaded to social media websites, and said to be shot in Idlib on Sunday showed emergency vehicles tackling blazes amid the rubble.
But it was not immediately clear what the nature of the attack was.
Idlib province is a stronghold of rebels in Syria and is situated on the border with Turkey, one of the main backers of rebellion against President Bashar al-Assad.
