Istanbul Mayor Ekrem Imamoglu was arrested on Wednesday as part of a corruption investigation, according to Turkish media.
He is also accused of being the leader of a criminal organization, rigging tenders and aiding a terrorist organization.
Local news media reported that a large group of security personnel surrounded Imamoglu's home before taking him into custody.
Early this morning, Imamoglu's media advisor Murat Ongun said in a post on X that he was being detained, but did not give a reason.
Imamoglu said in X that hundreds of police were in front of his house, adding that he would not give in and would continue to resist the pressure.
Turkish authorities have also ordered the arrest of around 100 other suspects, including journalists and businessmen, as part of the same corruption investigation.