Did my friend break his fast by masturbating during Ramadan without knowing? What should he do now?

I was talking to my friend and I told him that ihtilam does not break fast but masturbation breaks the fast, so he told me that he did not knew that masturbation breaks the fast and that he had done masturbation few times in Ramadan during fasting (not knowing that it breaks the fast), so now what he has to do? Should he make the qaza of those 3 or 4 fasts in which he masturbated? Can he pay kaffarah instead of having fasts? Please tell in detail what are his liabilities? Also note that it was not in his knowledge that fast would break due to this act.