At least 20 people, most of them rebel fighters, have been killed and dozens injured in a bomb attack near Syria's border with Turkey, reports say.
The UK-based Syrian Observatory for Human Rights said the blast occurred at the Atmeh crossing, in Idlib province.
Turkey's state-run Anadolu news agency said it took place during a "change of guard" among rebels in the area.
A news agency linked to so-called Islamic State (IS) said a suicide bomber had targeted a rebel convoy.
Turkish-backed rebel factions are currently battling IS militants in another border region further east.
The rebels are advancing on the town of Dabiq, which holds great symbolic value to the jihadist group as it is named in Islamic apocalyptic prophecies as the site of an end-of-times showdown between Muslims and their enemies.