Did Members of the US-Led Coalition Carry Out an Air Strike to Help ISIS? Russia Implies They Did

The Russians say that in addition to the US aircraft, 2 pairs of aircraft - ie. 4 aircraft in total - from 2 other countries that are also members of the US led coalition were also flying at the time of the air strike over Deir az-Zor, Syria.  The Russians have not actually said it was these aircraft that carried out the air strike. But they have pointed out that the US has failed to admit to the presence of these aircraft. They are asking why?  It is difficult to believe that the Russians do not think that it was these aircraft that carried out the air strike. Inevitably, that begs the question of whether the aircraft that carried out the air strike were providing air support to the fighters of the Islamic State.