Turkish authorities detained 357 suspects in a nationwide operation targeting the Islamic State group, Interior Minister Ali Yerlikaya said on Tuesday. The arrests followed a gunfight a day earlier in northwest Turkey in which three police officers and six suspected IS militants were killed. According to Yerlikaya, coordinated raids were carried out across 21 provinces.

Earlier statements from the Istanbul prosecutor’s office said police raided 114 addresses in Istanbul and two other provinces, seizing digital materials and documents. The clashes occurred during an eight-hour siege at a house in Yalova, south of Istanbul on the Sea of Marmara. Eight police officers and one other security personnel were wounded during the operation, which was part of a broader sweep involving more than 100 locations.

Turkey has intensified operations against suspected IS members in recent months. Authorities have cited concerns about planned attacks during the Christmas and New Year period, after more than 100 suspects were detained last week. Islamic State has previously been responsible for major attacks in Turkey between 2015 and 2017, including assaults on Istanbul’s main airport and a nightclub, after which security forces launched sustained counterterrorism operations that significantly reduced such incidents.