First Syria denied it, and then Russia denied it as well, though Israel is still insisting it is true.

Not having any way of knowing whom to believe, all I can say is I would completely understand why Russia and Syria must deny it.  Not that that tells us much. 

I would like to think that stepping up during such a time of crisis, even for an enemy, is a good thing and something that can perhaps effect a thawing of bad relations later when the crisis dies down. I dont know if it is true or fake news, but I can hope it is true and that something good will come out of it.