More than 200 detained in Turkey over Gulen links
Police detained 171 people in Ankara alone, while another 18 suspects, including 10 doctors, were sought in a second probe.
The detentions came after the capital's prosecutor issued arrest warrants for 260 people accused of using the encrypted ByLock messaging application which authorities believe was used to coordinate the coup bid.
Tens of thousands have been arrested over alleged ties to US-based Muslim preacher Fethullah Gulen who Ankara says ordered the failed coup. Gulen denies this.
Read also: Turkey offers $700,000 bounty for exiled Palestinian strongman Mohammad Dahlan
The main opposition Republican People's Party (CHP) said Burak Oguz, a mayor for Urla district in the Aegean region of Izmir, was arrested on suspicion of having Gulen links.
"We condemn using the pretence of law to remove elected officials. We support our mayor," Deniz Yucel, CHP chairman in Izmir, tweeted.
He added that the secular CHP had no ties to Gulen's Islamic network.
Oguz is the first CHP mayor to be arrested since March local elections, but dozens of officials from the pro-Kurdish Peoples' Democratic Party (HDP) have been arrested over suspected ties to Kurdish militants.
Four HDP co-mayors of Varto and Bulanik districts in the eastern Mus province were detained on Tuesday, the party said. They are accused of links to the Kurdistan Workers' Party (PKK), an insurgent group outlawed by Ankara and its Western allies.
A total of 28 HDP mayors have been removed from office since the election.
Following the failed overthrow of President Recep Tayyip Erdogan, authorities have also sacked or suspended over 140,000 public sector workers for suspected links to Gulen.