Image copyright AFP Image caption Reza Zarrab is testifying in a high-profile US Iran sanctions trial

A Turkish-Iranian gold trader testifying in a US trial of a Turkish banker says he has had death threats from another inmate for co-operating.

Reza Zarrab is a witness in the trial of Mehmet Hakan Atilla, who is accused of violating US sanctions against Iran.

Mr Zarrab told the court on Thursday that he was transferred from a Brooklyn prison to FBI custody, for protection.

In a separate development, Mr Zarrab, 34, was accused of sexual assaulting his 62-year-old cellmate last year.

Robert Anello, attorney for Mr Zarrab, said the assault allegations were "outrageous and false from a source that is not remotely credible".

On his last day of testimony at the trial, the trader said another inmate revealed to him that he had "received instructions to kill because I was co-operating".

Mr Zarrab did not identify the person or say when the threat was made. His account has not been confirmed by the US Bureau of Prisons.

He pleaded guilty in October to working with Mr Atilla in an attempt to help Iran evade US economic sanctions.

Turkish denials

Earlier in his testimony, he told the court that Turkish President Recep Tayyip Erdogan had approved his and the defendant's sanctions-breaking deals.

He implicated Mr Erdogan in an international money laundering scheme that he and the banker ran between 2010 and 2015, which allegedly allowed Iran access to global markets despite US sanctions.

He said that he was told in 2012 by the then economy minister that Mr Erdogan, who was prime minister at the time, had instructed Turkish banks to participate in the multi-million dollar scheme.

Mr Erdogan has denied that Turkey breached US sanctions, but the case has strained relations between Ankara and Washington. Turkish prosecutors have ordered the seizure of Mr Zarrab's assets.

Mr Zarrab was arrested by US officials in 2016, accused of engaging in hundreds of millions of dollars worth of transactions on behalf of the Iranian government, money laundering and bank fraud.

He later agreed to co-operate with the prosecutors in a case against Mr Atilla.

The sexual assault allegation against Mr Zarrab comes some months after the alleged incident. Faouzi Jaber, a former cellmate, alleges Mr Zarrab assaulted him some time between November 2016 and March 2017.

Asked why the allegation came so long after the alleged incident, Mr Jaber's attorney Alexei Schacht said he was only recently hired to be his lawyer and had "filed it as soon as possible".

The Federal Bureau of Prisons found the allegations to be "unsubstantiated", AFP reported.