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By Daren Butler

ISTANBUL, June 28 (Reuters) - Turkey will appoint a former head of Islamic lender Turkiye Finans as its new treasury undersecretary, Deputy Prime Minister Mehmet Simsek was quoted as saying on Tuesday, the third recent appointment of an Islamic banker to a top financial post.

The government in April appointed Murat Cetinkaya, who has spent his career in Islamic finance, as governor of the central bank. A year earlier, veteran Islamic banker Mehmet Ali Akben was appointed to oversee the country's $820 billion banking industry as head of the BDDK watchdog.

"Osman Celik is a successful economist with experience in the private sector," state-run news agency Anadolu quoted Simsek as saying on the Twitter feed of its AA Finans service.

The previous two appointments had already been seen as reflecting Ankara's drive to bolster Islamic finance, which prohibits the charging of interest. President Tayyip Erdogan, a pious Muslim, has worked to develop Islamic banking in Turkey.

Islamic banks account for about 5 percent of total banking assets in Turkey. The government last year presented a legal framework to encourage publicly owned Islamic banks and wants Islamic banks to double their assets to $100 billion by 2023.

The post of treasury undersecretary has not been formally filled since Ibrahim Canakci left to join the International Monetary Fund in 2014 after more than a decade in the post. A deputy had taken the role of acting undersecretary since then.

Born in 1964, Celik studied economics at Ankara's Middle East Technical University before working as an economist in the State Statistics Institute.

He entered banking in the late 1980s and took over in 2015 as general manager of Turkiye Finans, majority-owned by Saudi Arabia's National Commercial Bank.

Celik is also a board member of the TKBB association of Islamic finance banks, according to its website.

(Editing by Nick Tattersall) ((daren.butler@thomsonreuters.com; +90-212-350 7122; Reuters Messaging: daren.butler.thomsonreuters.com@reuters.net))