Beykoz Mayor Alaattin Köseler was detained on corruption and misconduct charges as part of an investigation conducted by the İstanbul Chief Public Prosecutor’s Office.
Köseler was taken into custody in a pre-dawn police raid and brought to the İstanbul Police Department for questioning. The case file, prepared by the İstanbul Chief Public Prosecutor’s Office and forwarded to the Beykoz Prosecutor’s Office, states that he is being investigated for “bid rigging” and “abuse of office.”
During the operation, police and riot control teams were stationed outside Beykoz Municipality, where security measures were tightened.
In addition to Köseler, the Beykoz Chief Public Prosecutor’s Office issued detention orders for four other suspects on bid rigging charges.
Authorities also ordered the detention, search, and seizure of assets for 17 other individuals under allegations of “forming, leading, or aiding a criminal organization” alongside bid rigging charges.
The mayor's detention could lead to his replacement by a government-appointed trustee.

Former Beykoz municipal official detained in investigation into concert spending
CHP condemns detention
The main opposition Republican People’s Party (CHP), to which Köseler belongs, strongly criticized the operation.
CHP İstanbul Provincial Chair Özgür Çelik denounced the mayor’s detention, emphasizing that it took place at 4:00 a.m. in a police raid at his home.
"He is a 65-year-old mayor with a known address who would testify when summoned. This treatment is yet another link in the chain of oppression," Çelik said in a social media post.
Çelik also suggested that the timing of the operation was politically motivated, taking place on the day İstanbul Mayor Ekrem İmamoğlu was set to deliver a high-profile speech in Ankara.
"This midnight, 'timed' operation is nothing more than an act of desperation by those trying to manipulate politics through the judiciary. Those who think they can stop CHP with such efforts are gravely mistaken. No matter what they do, CHP’s presidential candidate will be Turkey’s next president," he stated.
CHP Beykoz District Chair Mahir Taştan also reacted to the detention, calling on party members to gather in front of the Beykoz Municipality building in support of Köseler.
"We stand by our mayor and against every unlawful step taken. I invite all our members to defend our mayor in the municipal square," Taştan said.
Previous investigations into Beykoz Municipality
In January, the Beykoz Chief Public Prosecutor’s Office launched an investigation into V.G., the municipality’s chief of staff, following bribery allegations circulated on social media.
A Labor Ministry inspection in December found that around 20 municipal employees were working without insurance. Beykoz officials claimed these workers were "volunteers."
Authorities in November began investigating 20 million liras in alleged irregular spending related to three concerts and Beykoz Anadolu Spor AŞ’s participation in TFF 2. Lig.
A Feb 2022 probe into alleged mismanagement of advertising and announcement revenues led to an initial review by the İstanbul Governor’s Office, which found no grounds for further action. The Interior Ministry later dropped the case. The municipality was run by the ruling Justice and Development Party (AKP) before the 2024 local election.
CHP municipal council member Cemal Sataloğlu filed a criminal complaint in Nov 2021, claiming that the municipality had failed to collect advertising revenue, causing a 30 million lira loss. However, the Interior Ministry declined to assign an inspector to the case.
Investigations targeting CHP-run municipalities in İstanbul
The investigation into Beykoz Municipality comes amid a broader crackdown on CHP-run municipalities in İstanbul. In Oct 2024, Esenyurt Mayor Ahmet Özer was arrested on charges of "membership in an armed terrorist organization" due to alleged links to the outlawed Kurdistan Workers' Party (PKK). Following his arrest, he was removed from office, and İstanbul Deputy Governor Can Aksoy was appointed as a trustee mayor. Özer denied the allegations, stating that he expected his party to defend him.
In Jan 2025, prosecutors issued 47 arrest warrants as part of a corruption investigation into Beşiktaş Municipality. Among those detained was Beşiktaş Mayor Rıza Akpolat, who was accused of being involved in a bribery and rigged bidding scheme. He was arrested in Balıkesir and later transferred to İstanbul, where he was formally taken into custody.
İstanbul Mayor Ekrem İmamoğlu, who declared his intention to run as the CHP's presidential candidate, is also facing prison sentences and a ban from politics on several charges, including "attempting to influence the judiciary" and "targeting counterterrorism officials."
(VK)