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Aug 4 (Reuters) - Libya's National Oil Corporation said on Monday it signed a memorandum of understanding with U.S. oil giant ExxonMobil XOM.N after a decade of activity halt in the North African country due to security reasons.

NOC in a statement said the MoU focuses on conducting detailed geological and geophysical studies to identify the hydrocarbon resources in four offshore blocks located off the northwest coast and the country's Sirte Basin.

In 2013, ExxonMobil, the world's largest publicly-traded energy company, decided to cut back its staff and operations in Libya as growing instability no longer justified a major presence.

The company's decision then came amid growing concern among international oil companies that the returns on offer in Libya may not justify the security and political risks that had grown since the 2011 uprisings that swept the Middle East.

Libya's oil output has been disrupted repeatedly in the chaotic decade since 2014, when the country divided between two rival authorities in the east and west following the NATO-backed uprising that toppled Muammar Gaddafi in 2011.

(Reporting by Ayman al-Warfalli; Writing by Muhammad Al Gebaly; Editing by Bill Berkrot)

((Muhammad.AlGebaly@thomsonreuters.com;))