Gulen, who lived in the United States since 1999, was the bete noire of Turkish President Recep Tayyip Erdogan who accused him of heading a "terror organisation".

"Our intelligence sources confirm the death of the leader of the FETO organisation," Foreign Minister Hakan Fidan told a press conference, using Turkey's term for Gulen's influential Hizmet movement of schools, businesses and charities.

Turkey's TRT public television said the preacher, who had lived in Pennsylvania for a quarter of a century and was stripped of his Turkish nationality in 2017, died in hospital overnight.

Gulen moved to live in the United States in 1999, ostensibly for heath reasons. From there he ran Hizmet, a movement which has a sprawling network of public schools on every continent.

But the organisation has long been blacklisted by the Turkish authorities who refer to it as FETO, the Fethullah Terror Organisation (FETO).