SYDNEY - The head of the Bahrain-based Accounting and Auditing Organisation for Islamic Financial Institutions (AAOIFI) has resigned after more than three years at the helm of the standard-setting body.

Secretary General Hamed Hassan Merah told Reuters he had presented an "objectively reasoned resignation" to AAOIFI's board of trustees which in turn accepted it on Thursday.

Saudi-born Merah took the role in September of 2014, helping oversee the most significant overhaul of AAOIFI's activities since its establishment in 1990.

AAOIFI standards are used widely in the $2 trillion industry and are mandatory in several countries such as Bahrain and Oman.

But as a complex organisation with 200 institutional members from across 45 countries, it had been slow to respond to issues relating to conflicts of interest and product standardisation.

Under Merah, however, AAOIFI tackled such issues head on, launching a review of its accounting, auditing and sharia standards and fast-tracking several new ones.

AAOIFI reorganised its internal structure by appointing 50 members across three technical boards in late 2015, which included the creation of a board on governance and ethics.

That board developed a standard on central sharia boards, seen a key development to help unify industry practices.

AAOIFI also approved a standard for gold-based products, while it had started work on standards covering Islamic endowments, known as awqaf.

In November, Merah said AAOIFI would now prioritize wider adoption of its standards by engaging national regulators in key markets, including Turkey and Malaysia.

Saudi Arabia's central bank joined AAOIFI as an institutional member in October.

(Reporting by Bernardo Vizcaino; Editing by Simon Cameron-Moore) ((Bernardo.Vizcaino@thomsonreuters.com; Telf: +61293218168; Reuters Messaging: bernardo.vizcaino.thomsonreuters.com@reuters.net))