The identities exposed possible connections between Islamic State cells and Turkey’s large communities of workers and others from the Central Asia region. There has been no claim of responsibility for the attack, but Turkish officials have said they believe the Islamic State is behind the bloodshed…

Counterterrorism units raided 16 addresses in Istanbul and launched operations in the coastal city of Izmir, according to Turkish officials and the state-run Anadolu news agency.

Three of those arrested in Istanbul are foreign nationals. Another nine suspects were detained in Izmir for providing logistical support to the Islamic State, but it was unclear if they are directly tied to the attack…

“If the Islamic State is indeed behind this attack, this would be a declaration of war,” said Soner Cagaptay, director of the Turkish Research Program at the Washington Institute for Near East Policy. “This attack is different: the scope, impact and deaths of dozens in the heart of the country’s economic capital.