DUBAI, May 23 (Reuters) - Abu Dhabi National Oil Company

(ADNOC) raised $935 million from an additional

5.5% sale of shares in its drilling unit to institutional

investors, it said in a statement on Thursday.

The transaction, which was announced on Wednesday,

constitutes a sale of 880 million shares priced at 3.90 dirhams,

at a 5.6% discount to the closing price of 4.13 dirhams on May

22.

It follows ADNOC Drilling's IPO more than two years ago, when

the company priced shares at 2.3 dirhams a piece, raising $1.1

billion. The stock soared about 30% on its debut.

ADNOC said the transaction will increase the drilling unit's

free float to 16.5% and stands as the biggest accelerated

bookbuild of a publicly listed company in the UAE.

The energy firm will retain a majority 78.5% shareholding in

its drilling unit and has agreed to a restriction from selling

further shares for a period of six months, the statement said.

Increasing ADNOC Drilling's free float is expected to lead

to the company's inclusion in the Morgan Stanley Capital

International (MSCI) Emerging Market Index, ADNOC said. That

could happen at the next quarterly index review subject to ADNOC

Drilling meeting criteria, it added.

Egyptian investment bank EFG Hermes, First Abu

Dhabi Bank, Goldman Sachs ( GS ) and JPMorgan

Securities acted as joint global coordinators and

bookrunners for the offering.

The settlement of the offering is expected to take place on

or around May 28, ADNOC added.

($1 = 3.6726 UAE dirham)

(Reporting by Yousef Saba, Rachna Uppal and Federico Maccioni,

editing)