ISTANBUL — The suicide attacker who detonated a bomb that killed 10 German tourists in the heart of Istanbul's historic district had registered as a refugee just a week earlier, Turkish officials said Wednesday, raising questions over whether extremists are posing as asylum-seekers to inflame anti-immigrant sentiment in Europe.
Turkish authorities identified the assailant in Tuesday's attack as a Syrian man who was born in 1988, and said he was affiliated with the Islamic State group. Turkish media, including some close to the government, identified him as Nabil Fadli and said he was Saudi-born. The extremist group has not so far claimed the attack.
Meanwhile, Turkish police arrested five people suspected of direct links to the bomb attack which took place just steps from the historic Blue Mosque in Istanbul's storied Sultanahmet district. The suspects were not identified.
The bomber had recently entered Turkey, authorities said, and Interior Minister Efkan Ala confirmed reports he had registered with an Istanbul branch of the Migration Management Authority, providing fingerprints that allowed officials to quickly identify him. Ala said the bomber wasn't on any Turkish or international watch lists for IS militants.
"This person was not someone who was being monitored," Prime Minister Ahmet Davutoglu said. "It is a person who entered normally, as a refugee, as an asylum-seeker."
The attack wounded 15 people, including nine Germans and citizens of Norway, Peru and South Korea. Six of the victims remained hospitalized on Wednesday.
Although not as deadly as two attacks in Turkey last year that were blamed on IS, Tuesday's bombing had heightened resonance because it struck at Turkey's $30 billion tourism industry, which has already suffered from a steep decline in Russian visitors since Turkey shot down a Russian warplane near the Syrian border in November.
The fact that the bomber had registered as a Syrian refugee suggests central planning by Islamic State leaders, either to cover their tracks or provoke a backlash in Europe against legitimate Syrian asylum-seekers, said Firas Abi-Ali, an analyst with the security consultancy IHS Country Risk.
"It seems to make it less likely this was anything but a centrally commanded operation by the Islamic State," he said.
It is not the first time the group has taken advantage of the chaos caused by the huge influx of asylum-seekers into Europe by ensuring that suicide bombers were registered and fingerprinted — and would thus be identified as refugees after their deaths.
Two of the suicide bombers who died Nov. 13 at France's national stadium had registered in Greece — and their forged Syrian passports were found on their bodies.
Thousands of Muslims have fled the territory under Islamic State control in Syria and Iraq and the extremists have repeatedly threatened those who leave, saying they will regret their journey to Europe.
The Soufan security firm said in an analysis Wednesday that IS was not short on volunteers for suicide missions and the migrant crisis was posing a security challenge for Europe.
"Given how much time the Islamic State has had to administer explosives training in Raqqa, Mosul, and elsewhere, the group is likely not running low on bomb-makers or suicide mission volunteers," the firm said.
"The chaos on Europe's southern borders, involving a combination of overwhelming numbers of refugees, inadequate screening processes, and untold numbers of false travel documents, is a security challenge of the highest order."
In addition to the five people suspected of direct links to Tuesday's attack, more than a dozen other suspected IS militants were detained Wednesday and 59 a day earlier, although officials said none appeared to be tied to the Istanbul bombing.
They included three Russian nationals taken into custody in the Mediterranean coastal city of Antalya, a popular destination for tourists. The state-run Anadolu Agency said the suspects were allegedly in contact with IS fighters in conflict zones and had provided logistical support to the group.
Nearly 3,000 Russians, mostly from the predominantly Muslim North Caucasus, are believed to have gone to fight alongside IS militants in Syria. Families of IS recruits and human rights activists in the Caucasus have described Turkey as the main gateway to Syria for Russian fighters. Some IS fighters of Russian origin are believed to have left IS to settle in Turkey, families say.
On Wednesday, Davutoglu contended that in addition to the Islamic State group, other forces he did not identify were behind Tuesday's attack and were using the extremist group as a "pawn."
"We are working intensely to find the true actors in the background who are using this terror organization," Davutoglu said, without elaborating.
The Turkish premier said other countries fighting the Islamic State group had to adopt "a sincere stance," accusing Russia both of preventing Turkey from carrying out raids on the extremists and of bombing schools and hospitals in Syria instead of fighting IS.
Asked whether Turkey would retaliate for the attack with aerial strikes on IS positions, Davutoglu said: "I say this clearly, we would respond to every attack directed against us with the force we see fit."
Germany meanwhile, sent a team of investigators to Istanbul on Wednesday to support Turkish authorities investigating the attack.
German Interior Minister Thomas De Maiziere said there was no sign Germans were specifically targeted.
"According to the investigations so far, there are no indications that the attack was directed specifically against Germans, so there can't be any connection to our contribution to the fight against international terrorism," de Maiziere said.
Following the November attacks in Paris, Germany Committed Tornado reconnaissance jets to aid the military effort against the Islamic State group in Syria and started flying missions from the Incirlik air base in Turkey last week. It also sent a tanker aircraft, as well as a frigate to help protect a French aircraft carrier in the eastern Mediterranean.
Germany already was helping supply and train Kurdish forces fighting IS in northern Iraq but has not taken a direct combat role.
Those killed in Tuesday's blast included two couples. Authorities didn't identify the victims but said they ranged in age from 51 to 73.
Fraser reported from Ankara, Turkey. Associated Press writers Geir Moulson, David Rising and Frank Jordans in Berlin and Lori Hinnant in Paris contributed to this report.
A previous version of this story has been corrected to show that the German interior minister's surname is Maiziere, not Maziere.