Turkish prosecutors have opened an investigation after the Istanbul-based founder of a cryptocurrency exchange shut down his site and fled the country with a reported $US2 billion ($2.6 billion) in investors’ assets.

The Thodex website went dark after posting a mysterious message saying it was suspending trading for five days on Wednesday (local time) because of an unspecified outside investment.

Turkish security officials then released a photo of Thodex founder Faruk Fatih Ozer going through passport control at Istanbul airport on his way to an unspecified location.

Local media reports said Mr Ozer — reported to be either 27 or 28 years old — had flown either to Albania or Thailand.

HaberTurk and other media said Thodex shut down after running a promotional campaign that sold Dogecoins at a big rebate — but did not allow investors to sell.