ISTANBUL (Reuters) - Turkish authorities on Thursday detained 18 suspected Islamic State members in Istanbul and Izmir, two of Turkey biggest cities, officials said.

In an operation by Turkey’s intelligence agency and counter-terrorism police, 10 suspected militants were detained in the Aegean coastal province of Izmir, a security source said.

Eight more suspects were detained in Istanbul on Wednesday, police said. The suspects were thought be providing financial support to the organization, had traveled to and from conflict zones and been trained to carry out suicide bombings, it said. It added that three more suspects were still being sought.

Islamic State has carried out numerous bombings across Turkey in recent years, including an attack on a nightclub in Istanbul on Jan. 1, 2017, in which 39 people were killed and a bombing in the city’s historic heart that killed 12 in 2016.