[Source: Reuters - Supporters of Istanbul Mayor Ekrem Imamoglu gather near the city's police headquarters in Istanbul, Turkey]

Turkey detained Istanbul mayor Ekrem Imamoglu, the main rival of President Tayyip Erdogan, on charges of corruption and aiding a terrorist group in what the main opposition party on Wednesday called “a coup against our next president“.

The move against the popular two-term mayor caps a months-long legal crackdown on opposition figures across the country which has been criticised as a politicised attempt to hurt their electoral prospects and silence dissent.

Turkey’s lira currency crashed as much as 12% to an all-time low of 42 to the dollar in response, underscoring worries over the eroding rule of law in the major emerging market and NATO member country that Erdogan has run for 22 years.

Imamoglu, 54, who leads Erdogan in some opinion polls, was to be named his Republican People’s Party’s (CHP) official presidential candidate within days. He now faces two separate investigations that also include charges of leading a crime organisation, bribery and tender rigging.

In a handwritten letter shared on social media, the detained mayor said Turks would respond to the “lies, plots and traps” against him. Earlier, before leaving home for the police station, he said he would not give up in the face of pressure.

Justice Minister Yilmaz Tunc warned against linking Erdogan to Imamoglu’s detention or other legal processes, using words like “coup” to describe it, and also against street protests.

Though authorities temporarily banned protests and police shut down some city streets, some hundreds of people gathered at the police station and chanted: “The day will come when (Erdogan’s) AK Party is called to account”.

Thousands gathered in Istanbul’s Sarachane district later on Wednesday, while CHP leader Ozgur Ozel addressed crowds near the municipality building, saying Erdogan had targeted Imamoglu due to fears of losing to him in the ballots.

“Today, Tayyip Erdogan is trying to break Ekrem Imamoglu’s wrist, which he could not bend three times, with the stick of the judiciary,” Ozel said, referring to municipal election losses suffered by Erdogan and his AKP against Imamoglu and the CHP.

“I am challenging you from here. Are you up for it Erdogan? Are you up for coming before us?,” he added.

Several hundred others protested the detention at the Middle East Technical University (METU) in Ankara and chanted anti-government slogans, while police fired tear gas to disperse them. Scattered protests and gatherings also took place in other cities, including Izmir and Trabzon.

Any further protests could test authorities’ willingness to expand a legal blitz since late last year that already includes numerous indictments, the ousting of several elected opposition mayors and the jailing of a nationalist party leader.

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