American prosecutors have charged a senior executive at state bank Halbank with participating in a multi-year scheme to violate US sanctions against Iran.
Halkbank confirmed on Wednesday that Mehmet Hakan Atilla, its deputy general manager, had been detained in the United States and said it and the Turkish government were working on the issue.
Atilla is accused of conspiring with wealthy Turkish gold trader Reza Zarrab to conduct hundreds of millions of dollars of illegal transactions through US banks on behalf of Iran's government and other entities in that country.
"Our bank and relevant state bodies are conducting the necessary work on the subject and information will be shared with the public when it is obtained," Halkbank said in a statement.
Shares in the Turkish state lender plunged as much as 16 percent on Wednesday.
Turkish Foreign Minister Mevlut Cavusoglu said the case would be discussed with US Secretary of State Rex Tillerson when he visits Ankara this week. Cavusoglu, speaking to broadcaster TRT Haber, also called for a transparent process regarding Atilla's arrest.
The arrest of the 47-year-old banker escalates a case that has added to the tensions between the United States and Turkey. President Recep Tayyip Erdogan has previously said he believed US authorities had "ulterior motives" in prosecuting Zarrab, who was arrested in March 2016 in Miami.
Zarrab has denied the charges in his case. It was unclear whether Atilla has hired a lawyer or made a bail application.
