Turkish authorities have arrested more than 120 municipal officials in Izmir, a key stronghold of the opposition, over allegations of corruption, local media and the opposition Republican People’s Party (CHP) reported on Tuesday.

The arrests follow a similar high-profile operation in Istanbul on March 19, which led to the detention of the city’s popular mayor, Ekrem Imamoglu — widely seen as the main political rival to President Recep Tayyip Erdogan.

According to CHP vice president Murat Bakan, those detained in Izmir include a former mayor and several senior city hall officials.

Izmir, Turkey’s third-largest city, has been governed by the opposition for decades and remains a major base of support for the CHP.

In total, some 157 arrest warrants were issued in the operation, local media reported.

“We are faced with a process similar to that in Istanbul,” Bakan wrote, adding that Tunc Soyer, a former mayor, and Senol Aslanoglu, the party’s regional president, were among those detained.

“These dawn arrests were not a legal obligation, but a clear political choice,” Bakan wrote, saying that many of those detained had already been under investigation.

“If they had been called to testify, they would have done so,” he said.