Isn't he the same God as in the New Testament? Funny how you left that part out!
Funny, isn't it? The omniscient, omnipotent, never-changing God seems to have gotten a lot more peaceful after Christ. But even the NT proscribes nasty punishment for the unbelievers. This punishment is done by God and angels, but then in the OT the Jews taking a city is always credited to God. Someone who wanted to do violence according to the NT could also use passages to validate it.
Allah is NOT the God of the Old and New Testament.
(The name and symbolism of "Allah" is actually derived from the Moon god of the Egyptians, but that is a different discussion...)