At least 21 fighters from a Syrian Islamist rebel group were killed on Sunday in an attack on a village in Syria's northwestern province of Idlib.Two explosions rocked a base belonging to the Ahrar al-Sham rebel group in the village of Tell Touqan, located east of Idlib, Efe quoted the Syrian Observatory for Human Rights as saying.Among the dead was a commander of Ahrar al-Sham, one of the main rebel organisations in Syria.The remains of two people, suspected of being the suicide bombers who targeted the base, were also found at the scene of the attack.In a message posted on Telegram, Ahrar al-Sham blamed the Islamic State (IS) terror organisation for the attack.Neither IS nor any other group, however, has claimed responsibility for the attack.Almost all of Idlib is controlled by Islamist and rebel groups, including Ahrar al-Sham, which usually operates with Jabhat Fateh al-Sham, the former al-Qaeda affiliate in Syria.