DUBAI - Morgan Stanley's regional head for the Middle East and North Africa (MENA) Sammy Kayello is stepping down, the bank said in an internal memo, though he will remain with the business as a senior adviser at the Wall Street bank.

Morgan Stanley's chief executive for Saudi Arabia Abdulaziz Alajaji and the bank's head of investment banking for MENA Patrick Delivanis will succeed Kayello as regional co-heads of MENA, the internal memo distributed on Friday said.

The U.S. bank said Alajaji and Delivanis will keep their existing roles as well as taking on their expanded responsibilities.

Bloomberg first reported the regional management changes at the bank. Morgan Stanley declined to comment when contacted by Reuters on Monday.

The memo, seen by Reuters, also said Gokhan Unal will become MENA vice chairman at the U.S. bank, in addition to his existing leadership responsibilities in Morgan Stanley's investment management business.

(Reporting by Hadeel Al Sayegh; editing by Barbara Lewis)