More from Turkish prime minister Davutoglu ("Daesh" is an Arabic acronym for the IS group).
The Istanbul suicide bomber "recently entered Turkey from Syria," Turkish Deputy Prime Minister Numan Kurtulmus has said.
All of the people killed in this morning's suicide bombing in Istanbul were foreign nationals, Turkish Prime Minister Davutoglu has said.
Syria's Istanbul-based opposition coalition, the National Coalition, has condemned the suicide bombing in Sultanahmet Square in an online statement.
The United States has backtracked on its position over Syria, softening its stance to accommodate Russia, opposition coordinator Riad Hijab has said, Reuters reports.
Hijab was chosen in December as coordinator of the opposition negotiating body for future peace talks with the Syrian government.
Turkish President Erdogan has criticized Russia's intervention in Syria, saying that Moscow is laying the groundwork to create a "boutique" state in Syria around the northern province of Latakia, including by carrying out attacks against ethnic Turkomans there.
Erdogan's comments came as Syrian government forces advanced into the rebel stronghold of Salma in Latakia today.
IS militants in the town of Bin Jawad in Libya have killed five Libyans, Libya's Al Wasat is reporting.
The five men were reportedly killed in Bin Jawad's public square on January 11 on charges of collaborating with Libya's military.
IS overran Bin Jawad on January 4.
Turkey analyst Aaron Stein has these comments about the suicide bombing in Istanbul today.