A batch of 75 rebels newly trained by US and coalition forces in Turkey to fight jihadists have entered northern Syria, a monitoring group told AFP on Sunday.

"Seventy-five new fighters trained in a camp near the Turkish capital entered Aleppo province between Friday night and Saturday morning," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

He said the group had entered in a convoy of a dozen cars with light weapons and ammunition, under air cover from the US-led coalition that has been carrying out air strikes against the Islamic State group in Syria and Iraq.

The fighters then deployed to support two US-backed units, with most assigned to Division 30 -- the main unit for US-trained fighters -- and others to a group called Suqur al-Jabal (Falcons of the Mountain).

Before the new batch of fighters, the US-led train-and-equip programme had only managed to identify and train some 60 rebels to fight IS jihadists on the ground.

The $500 million programme run out of Turkey has been fraught with problems, with more than a dozen of those already deployed with Division 30 either dead or kidnapped.