A UN board of inquiry says it has received reports that an attack on an aid convoy on the outskirts of Aleppo in September was "highly likely" to have been carried out by the Syrian air force but it was unable to reach a definitive conclusion.

A summary of the board's report released late Wednesday by Secretary-General Ban Ki-moon says it "did not have evidence to conclude that the incident was a deliberate attack on a humanitarian target."

The board said an air attack using multiple types of munitions from more than one aircraft damaged or destroyed 17 trucks in the convoy, killing at least 10 people including five drivers and injuring at least 22 others.

Ban said the board was not allowed to visit the scene of the attack.