Turkey will take the necessary diplomatic and legal steps regarding the arrest of a top banker from Turkey's Halkbank, an adviser to President Tayyip Erdogan said on Thursday.

An executive from Turkey's fifth-largest listed bank by assets, Halkbank, is accused of conspiring with Turkish-Iranian gold trader Reza Zarrab, who is already on trial. Turkey's justice minister had said earlier the arrest was a "completely political" move.

Speaking at an interview with broadcaster NTV, presidential adviser Cemil Ertem also said he expected Turkey's economic growth to exceed 2.5 percent in the final quarter of 2016.