Syria's al-Nusra releases three US-trained rebels
Local media activist Jaber Abu Mohammad told The New Arab that those released included Zaher al-Ahmad, a commander in Division 13.
"All the Division 13 detainees have now been freed with the release of these three," Abu Mohammad added.
Al-Nusra Front had last month seized a number of bases from Division 13 in Maarat al-Numan, looting US weapons in the process including TOW anti-tank missiles.
The Syrian Observatory for Human Rights said al-Nusra also seized armored vehicles, a tank, and other arms in addition to taking a number of FSA prisoners.
Division 13 has made several pleas for the release of its fighters, while families of the detained men organised several protests in front of al-Nusra sites in Idlib's countryside.
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Tensions between al-Nusra and the FSA in Idlib have escalated following the Russian military withdrawal and the protests against the regime that took place after the declaration of a ceasefire.
Al-Nusra affiliates have made repeated attempts to clear demonstrations, accusing protesters of spreading "secular concepts" such as democracy and music.
Meanwhile, observers fear that al-Nusra might be planning to take control of Idlib in a repeat to the Raqqa scenario, when the Islamic State group (IS) took control and declared an "Islamic state" nearly two years ago.