ANKARA (Reuters) - Turkish authorities have ordered the arrest of gold trader Reza Zarrab, a prosecution witness in the New York trial of a Turkish banker, over unlawful building work, Anadolu news agency said on Monday.

Zarrab, 34, a dual national of Iran and Turkey, was a government witness in the trial of Mehmet Hakan Atilla, a former deputy general manager at Turkey’s state-owned Halkbank who was convicted of helping Iran evade U.S. sanctions.

On Monday, Anadolu said an Istanbul court had ordered the arrest of Zarrab for carrying out unlawful restorations at his villa in Istanbul’s Beykoz district, as part of the case in which he faces up to three years in prison.

Zarrab was detained in the United States in 2016 and last year pleaded guilty to charges that he schemed to help Iran evade U.S. sanctions. He then testified for the prosecution in Attila’s trial.

It was not clear whether Turkish authorities could act on the new warrant until Zarrab is freed from U.S. detention.

Anadolu said the Istanbul judge had asked the foreign ministry, justice ministry and Turkey’s consulate in New York look in to Zarrab’s legal status.

The case of Halkbank has been one of the main points of disagreement between Ankara and Washington, whose relations have plunged into crisis this year over a host of issues, including policy in Syria and Turkey’s defence purchases.

Halkbank denies any wrongdoing and President Tayyip Erdogan has condemned the court case as a political attack on his government. On Saturday, Erdogan, without giving details, said he had discussed the issue of Halkbank with U.S. President Donald Trump, helping the bank’s shares surge on Monday. [nA4N1WE005]