A mayor from Turkey’s main opposition party has joined President Tayyip Erdogan’s ruling Justice and Development Party (AKP) amid a broader crackdown on opposition figures in recent months.

Ozlem Cercioglu, who has served as mayor of the western city of Aydin since 2009 and was previously a lawmaker for the Republican People’s Party (CHP), announced her resignation from the CHP on Thursday, citing disagreements with the party’s leadership.

"Despite repeatedly seeking solutions to the problems we face within the CHP, we have unfortunately been unable to reach a resolution. I am no longer on the same path as the CHP," she wrote in a post on X.

Later the same day, Cercioglu formally joined the AKP at a ceremony attended by Erdogan, alongside three district mayors who had also defected from the CHP.

Concurrently, Turkish police detained 40 individuals in Istanbul, an opposition stronghold, including the mayor of the central Beyoglu district and several senior advisors, according to local media reports.

Wider context

The move comes amid a wave of investigations targeting opposition politicians, including Istanbul Mayor Ekrem Imamoglu, Erdogan’s chief political rival, over allegations of corruption and links to terrorism.  

The CHP has rejected the charges, describing them as politically motivated efforts to eliminate a democratic alternative, an accusation the government denies.

CHP leader Ozgur Ozel told reporters, without offering evidence, that AKP officials had pressured Cercioglu with threats of legal action and arrest unless she switched allegiance to the ruling party.

AKP deputy chair Hayati Yazici dismissed Ozel’s remarks as "completely untrue|'.

"Anyone who violates the law or commits a crime would eventually be brought to justice," Yazici told private broadcaster TV 100.

Speaking at the joining ceremony, Cercioglu also rejected the allegation, insisting she had not been intimidated by the prospect of any investigation.

Erdogan crackdown on Opposition intensifies: 500+ CHP figures detained

Turkish President Recep Tayyip Erdogan has lately launched an extensive crackdown on his main political opponents, with more than 500 members and affiliates of the Republican People's Party (CHP) detained over the past months.

Last month, Erdogan described the ongoing probe as an effort to dismantle a sprawling network of corruption, likening it to “an octopus whose arms stretch to other parts of Turkey and abroad.” However, critics say the operation reflects the deepening political repression aimed at dismantling the primary democratic alternative to Erdogan’s rule.

The investigation, which began in Istanbul, has expanded nationwide and focuses exclusively on municipalities governed by the CHP, the party founded by modern Turkey’s secularist leader, Mustafa Kemal Atatürk. The CHP has denied all corruption allegations, accusing the government of exploiting the judiciary to marginalize opposition voices.

Among those targeted are at least 15 elected mayors, including Istanbul Mayor Ekrem Imamoglu, widely seen as Erdogan’s leading political rival. More than 200 CHP members or local officials have been jailed pending trial. Analysts say such sweeping action has not been witnessed since the coups of the 1960s, 1970s, and 1980s.

Read more: 'Never lose hope', Istanbul mayor tells supporters amid arrest