Praise be to Allaah.
Undoubtedly their jihaad is for the sake of Allaah, because they are fighting the kaafir aggressors who are trying to put an end to Islam and destroy the Muslims. The mujaahideen have been given a right to some of the zakaah, as Allaah says (interpretation of the meaning), “As-Sadaqaat (here it means Zakaah) are only for…and for Allaah’s cause (i.e., for mujaahideen – those fighting in the holy battles)…” [al-Tawbah 9:60]. So zakaah is permissible for them, even if they are fighting in self-defence, because they are Muslims and their enemies are kuffaar. Zakaah and charitable donations given to them should be increased. And Allaah knows best.