Turkish police detained 90 people on Tuesday over suspected links to outlawed Kurdistan Workers' Party (PKK) rebels, the government said, and the main pro-Kurdish party decried the arrests as a politically motivated crackdown.
The operation across eight provinces was continuing, the Interior Ministry said in a statement.
The arrests come days after President Tayyip Erdogan warned he would replace any mayors elected in next year's local elections if they were deemed to have links to terrorism.
Erdogan accuses the main pro-Kurdish party, the Peoples' Democratic Party (HDP), of links to the PKK. The HDP denies this and says it is unjustly targeted by the government.
More than 140 HDP members had been detained over several days, the party said on Sunday.
Ninety-four of 102 municipalities in Kurdish-majority cities and towns are now administered by trustees, rather than their elected mayors. Authorities removed those mayors, elected in the last municipal elections in 2014, in the security crackdown that followed an attempted military coup in 2016.
"Elections are nearing," Erdogan said at a meeting of his AK Party (AKP) over the weekend, referring to the March 2019 local vote. "If those involved with terror come out of the ballot box, we shall appoint trustees without delay."
One prominent HDP lawmaker, Garo Paylan, said the arrests were politically motivated, and were part of the AKP's campaign strategy for the 2019 election.
"The AK Party has started its local election campaign from Diyarbakir by detaining journalists, politicians and theologians," Paylan said on Twitter. Diyarbakir is the largest city in the mainly Kurdish southeast.
The autonomy-seeking PKK, deemed a terrorist organisation by Turkey, the United States and Europe, has waged an insurgency against the state since 1984. Violence across the southeast escalated after the collapse of a ceasefire in 2015.
Turkey has in recent months conducted regular strikes on PKK bases in northern Iraq, especially the insurgents' stronghold in the Qandil mountains, where Ankara has also threatened to carry out a ground offensive.