A mayor from Turkey's main opposition Republican People's Party (CHP) was arrested over suspected links to the network that Ankara says orchestrated a failed coup in 2016, a party official said early on Tuesday.
Ankara has cracked down on suspected followers of Fethullah Gulen, a US-based cleric, since the July 2016 coup attempt in which some 250 people were killed. Operations against the network are still routine.
Burak Oguz, the mayor of Urla district in the Aegean coastal province of Izmir, is the first local authority from the CHP to be arrested since elections in March, reported Reuters.
Separately, Ankara has removed 28 co-mayors from the pro-Kurdish People's Democratic Party (HDP) due to alleged links to Kurdish militants. Twenty-two co-mayors have been arrested since August and 19 remain in pre-trial detention, according to the HDP.
Deniz Yucel, head of the CHP's Izmir provincial group, said on Twitter that Oguz had been arrested and rejected the accusation that the mayor belonged to any Gulen network.
"There is no chance for FETO to survive within the CHP," he said, using a word that commonly refers to the network. The party condemns the judiciary removing from office those who were elected, he said.
The Urla municipality did not immediately comment.
Gulen has lived in self-imposed exile in Pennsylvania since 1999. He has denied any involvement in the coup attempt.
In the three years since the attempt, more than 77,000 people have been jailed pending trial and about 150,000 civil servants, military personnel and others have been sacked or suspended from their jobs.
Turkey's Western allies and rights groups have criticized the scale of the crackdown, saying President Recep Tayyip Erdogan has used the abortive coup as a pretext to quash dissent.
Ankara has defended the measures as a necessary response to the scale of the security threat Turkey faces, vowing to eradicate Gulen's network.