(Adds quotes from chief executive)

ABU DHABI, May 12 (Reuters) - Abu Dhabi National Oil Company (ADNOC) said on Thursday it had reshuffled its leadership, in the first major shakeup since the appointment of Sultan Al Jaber as its chief executive in February.

ADNOC named Abdulaziz Abdulla Alhajri as director of its refining and petrochemicals division and Omar Suwaina Al Suwaidi as director of its gas division, it said in a statement.

The firm also appointed new chief executives for six of its 18 operating units, including Adco and Adma-Opco, the joint ventures responsible for most of the emirate's oil production.

The appointments are all promotions from within ADNOC's ranks, following the retirement of two executives.

"These new appointments reflect our commitment to strengthening and advancing our company by promoting talent from within," Al Jaber said in an emailed statement.

"They will also play a fundamental role in executing our strategic imperatives of creating a more profitable upstream business and a more valuable downstream business, ensuring more gas supply, and developing world-class talent," he said.

ADNOC is currently in talks to award stakes in its 40-year onshore concession to develop the emirate's biggest oilfields, after a deal with Western oil companies dating back to the 1970s expired in January 2014.

(Reporting by Maha El Dahan, writing by Katie Paul; editing by Nerijus Adomaitis and David Evans) ((Katie.Paul@thomsonreuters.com;))