Turkish President Recep Tayyip Erdogan on Saturday condemned the "heinous terrorist attack" in a Moscow concert hall that left 115 people dead.
Turkey has growing ties with Russia and Erdogan often speaks on the phone with President Vladimir Putin as he seeks to mediate between Moscow and Ukraine.
"We strongly condemn this heinous terrorist attack targeting innocent civilians," Erdogan told a public rally in the capital Ankara.
"Terrorism is unacceptable no matter who it comes from or who the perpetrator is."
Erdogan said Turkey shared Russia's pain, adding: "We'll continue to fight against terror, the common enemy of the humanity."
Russia on Saturday said it had arrested 11 people -- including four gunmen -- over the Crocus City Hall attack claimed by the Islamic State.