Turkish President Recep Tayyip Erdogan said a Tuesday blast that killed 10 when it ripped through a popular tourist area in central Istanbul has "Syrian roots," further proof Turkey is not immune to the troubles plaguing its southern neighbor.
Erdogan did not specify which group, specifically, his government thinks is responsible for Tuesday's explosion, which happened between the Hagia Sofia and Blue Mosque tourist attractions in the cultural and historic heart of the city. And no group immediately claimed responsibility.
Yet it's no secret ISIS and various militant factions have been battling in Syria, with Turkey siding against those groups.
At least 15 people were wounded in the explosion around 10:20 am (3:20 a.m. ET), the Istanbul governor's office said. The city's Sultanahmet Square, already a heavily guarded area, was swarming with security forces and ambulances in its aftermath.
"Investigations continue about the explosion's cause, the explosive's types, the perpetrator or perpetrators of the event," said Istanbul governor Vasip Sahin. Officials feared the toll -- of both dead and wounded -- may include foreign nationals.
A Norwegian citizen was taken to a nearby hospital after the incident, foreign ministry spokesman Frode Andersen told CNN. And Germany's foreign affairs ministry said "it cannot be ruled out that German citizens have become victims." Germany's Foreign Office issued a travel advisory, following the blast. Turkey is a popular destination for German tourists.
"Travelers in Istanbul are urged to avoid larger gatherings, also in public squares and to avoid tourist attractions for now," a statement said.
"Seems to be an attack of some kind'
The blast comes at a time Turkey is dealing with multiple threats to its security.
"This does seems to be an attack of some kind," said Sajjan Gohel, the international security director at the Asia Pacific Foundation. "There's been concern in Turkey for a while. Turkey's been on higher alert."
ISIS and the Kurdish group the PKK have been mentioned in recent outbreaks of violence. In October, two explosions hit a lunchtime peace rally in Ankara, which called for an end to the renewed conflict between the Kurdistan Workers' Party, or PKK, and Turkish government. More than 100 people were killed and more than 240 were injured.
ISIS is active in neighboring Iraq. The Turkish government allows the United States to launch strikes on ISIS positions from Incirlik Air Base in southern Turkey.
"The Islamic State has been unhappy with Turkey's cooperation with the United States," said Fadi Hakura, associate fellow at Chatham House. Kurdish forces have been battling ISIS across a swath of northern Iraq and Syria.