Interior Minister Ali Yerlikaya said eight police officers and another security force member were wounded during a raid on a property in the town of Yalova, on the Sea of Marmara coast south of Istanbul.
More than 100 addresses were raided nationwide early on Monday as part of the operation.
Turkey has stepped up operations against suspected Islamic State militants this year as the group has returned to prominence globally.
The United States carried out a strike against Islamic State militants in northwest Nigeria last week, while Australian police said two gunmen who attacked a Hanukkah event at Sydney’s Bondi Beach earlier this month appeared to have been inspired by the group.
On Dec. 19, the US military launched large-scale strikes against dozens of Islamic State targets in Syria in retaliation for an attack on American personnel.
Raid lasted hours
Police raided the house in Yalova on suspicion militants were hiding there overnight. Sporadic gunfire was heard during the operation, which lasted nearly eight hours, according to a Reuters photographer at the scene.
Last week, Turkish police detained 115 suspected Islamic State members whom authorities said were planning attacks on Christmas and New Year celebrations in the country.
Yerlikaya said the militants killed in Monday’s clash were all Turkish citizens, adding that five women and six children were brought out of the property alive.
In the past month, police have arrested a total of 138 Islamic State suspects and carried out simultaneous operations on Monday morning at 108 different addresses in 15 provinces, he said.
In a post on X, President Tayyip Erdogan offered condolences to the families of the police officers killed and said Turkey’s fight against “the bloody-handed villains who threaten the peace of our people and the security of our state” would continue “both within our borders and beyond them.”
Wave of IS attacks in 2015-2017
Police sealed off roads leading to the house in the early hours of Monday. Smoke was visible rising from a nearby fire, while a police helicopter flew overhead.
The Istanbul chief prosecutor’s office said last week that Islamic State militants were planning attacks targeting non-Muslims in particular.
Nearly a decade ago, the jihadist group was blamed for a series of attacks on civilian targets in Turkey, including gun attacks on an Istanbul nightclub and the city’s main airport, killing dozens of people.
Turkey was a key transit point for foreign fighters, including Islamic State members, entering and leaving Syria during the civil war there.
Police have continued regular operations against the group in subsequent years, and there have been relatively few attacks since the wave of violence between 2015 and 2017.