I have a better idea: we capture them, then try and execute them under Sharia law.
IIRC the punishment for murder is either an eye for an eye, or straight up hanging. That's boring. I say we apply the punishment used for adulterers; if anything these Middle Easterns are quite creative at preventing people from boning.
I think that might be the wrong approach.
A straight up, no fanfare, bullet in the head wherever they happen to be found and toss them in the nearest garbage bin. Do it without any anger or hatred, just cold clinical detachment. Deal with them as you would a rat or fly that is bothering you. Remove any notion of honor or nobility to them or their cause, and treat them as the vermin they are.
Nobody roots for the rats, if you can frame them as such by their own countrymen their support will dry up.