CAIRO, Sept 17 (Reuters) - Egyptian police arrested Muslim Brotherhood spokesman Gehad El-Haddad on Tuesday, three security officials said, a high-profile detention in the army-backed authorities crackdown on the Islamist movement.

Haddad was arrested with two other Brotherhood officials in an apartment in Cairo. Haddad served as chief of staff to deputy Brotherhood leader Khairat El-Shater and is the son of Essam El-Haddad, the foreign affairs adviser of deposed President Mohamed Mursi. (Writing by Tom Perry; Editing by Alison Williams)