U.S. authorities on November 7 indicted the brother of a wealthy gold trader who faces trial in January for violating sanctions by helping Iran transact business.
Mohammad Zarrab, who like his brother Reza is a dual citizen of Turkey and Iran, was charged with conspiracy in the prohibited transactions.
The indictment added new charges against Reza Zarrab, saying his illicit business benefited Iran's Mahan Air, which is targeted with U.S. sanctions for providing services to Iran's Quds Force and Hizballah.
Reza Zarrab was arrested in Florida in March. Mohammad Zarrab, 38, owns Flash Doviz Exchange and other money-service companies in Turkey, and remains at large, prosecutors said.
The case has drawn much attention in Turkey, where prosecutors in 2013 charged Reza Zarrab with paying cabinet officials bribes to facilitate transactions benefiting Iran.
Turkish President Recep Tayyip Erdogan, who was then prime minister, portrayed the case as a coup attempt orchestrated by his political enemies.
Several prosecutors were removed from the case, police were reassigned, and the investigation was dropped.
In September, Erdogan, whom prosecutors say had close ties to Reza Zarrab, said he believes U.S. authorities have "ulterior motives" in pursuing their case against Zarrab.
With reporting by Reuters