Turkey added cryptocurrency trading platforms to the list of firms covered by anti-money laundering and terrorism financing regulation, it said in a presidential decree published early on Saturday.
The Official Gazette said the country's latest expansion of rules governing cryptocurrency transactions would take immediate effect and cover "crypto asset service providers", which would be liable to the existing regulations.
Last month Turkey's central bank banned the use of crypto assets for payments on the grounds such transactions were risky. In the days that followed two Turkey-based cryptocurrency trading platforms were halted under separate investigations.
The probe into one of them, Thodex, led to the jailing on Thursday of six suspects including the siblings of its chief executive, Faruk Fatih Ozer, who Turkish authorities are seeking after he traveled to Albania
The six people formally arrested included Ozer's brother and sister, as well as senior company employees, the spokeswoman for Istanbul's Anadolu prosecutor's office said, Reuters reported.
Most of those detained over the past week have been released. Others, including seven on Thursday, were let go with judicial control measures.
The Thodex platform, which had been handling daily crypto trade worth hundreds of millions of dollars, said on its website last week it would be closed for four to five days due to a sale process.
Interior Minister Suleyman Soylu said this week Turkey sent units to four countries to search for Ozer, including Albania.
"When he is caught with the red notice, we have extradition agreements with a large part of these countries. God willing he will be caught and he will be returned," he said in a televised interview with broadcaster NTV.
Users and media reports had claimed Ozer could have run off with $2 billion but Soylu said the company's portfolio totalled $108 million.
Separately on Monday, authorities jailed four people pending trial as part of an investigation into Vebitcoin, another cryptocurrency trading platform.
