By Orhan Coskun
ANKARA (Reuters) - Nabil Fadli, a Saudi-born Syrian who killed 10 German tourists in a suicide bombing in Istanbul, was planning a major attack on New Year's Eve celebrations in Ankara but changed targets after the plot was foiled, two senior Turkish officials have told Reuters.
Fadli, born in Saudi Arabia in 1988 where his father was teaching, fought in the ranks of Islamic State in Syria and was at one stage captured and tortured, possibly by a Syrian Kurdish militia, before entering Turkey last month, the officials said. A Kurdish official in Syria denied he had entered Kurdish hands.
Fadli registered as refugee with authorities in Istanbul on Jan. 5 before blowing himself up a week later among groups of tourists in Sultanahmet Square near the Blue Mosque and Hagia Sophia, striking at the heart of Turkey's tourism industry.
Turkish tanks and artillery have bombarded Islamic State positions in Syria and Iraq in response to Tuesday's attack and Prime Minister Ahmet Davutoglu has vowed air strikes will follow if necessary.
Officials working to piece together Fadli's movements before the bombing said his plans had changed after two of his accomplices were caught preparing a suicide attack on a square in Ankara where crowds gather to celebrate the New Year.
At the time, Fadli himself had not raised any red flags with the authorities because he was not on any Turkish or international watch lists of militant suspects.
"He was in a group which was planning in particular a big attack for New Year’s Eve celebrations in Ankara. After the Ankara police unit’s work ... we think he changed cities to carry out a different attack," a senior security official said.
Two suspected Islamic State members thought to have been preparing an attack on Ankara's Kizilay square were detained on Dec. 30, a government source said at the time.
Turkey's intelligence agency shared information gathered as a result of those arrests with counterparts in several countries. The security official said the shared information had helped to foil other attacks being planned in Europe.
This assertion could not be verified, but several European countries tightened security at their New Years' celebrations, with German police evacuating two train stations in Munich, citing a tip about a planned suicide bomb attack, and Belgium holding three people over an alleged plot.
Four other people who registered with the authorities in Istanbul on Jan. 5 alongside Fadli have also been detained and are thought to have been part of a team that planned the attack, the senior Turkish security official said.
It was not clear why Fadli registered with the authorities days before carrying out the bombing, but some officials have suggested a deliberate attempt to complicate Turkish and European efforts to cope with the influx of Syrian refugees.
Attacks in Paris on Nov. 13 which killed 130 people had already raised fears in Europe about Islamist militants entering undetected among the hundreds of thousands of people fleeing war and poverty in countries including Syria and Iraq.
TORTURED IN SYRIA
Fadli's movements in Syria in the months before he entered Turkey on Dec. 18 are unclear, but Turkish officials said there was no question he had fought in the ranks of Islamic State.
His father's job as a teacher took the family to Saudi Arabia, where Fadli was born, but they returned to Syria after his father's work there ended. Saudi Interior Ministry spokesman General Mansour Turki said Fadli had not returned to Saudi Arabia since leaving the country in 1996.
In a posting on Facebook, a man identifying himself as Mohammad Bakir Hussein, a dental technician who had been at the same institute as Fadli, said his mother was from Aleppo and of Armenian origin and that he had lived in the Islamic State-held town of Manbij.
Hussein described Fadli, who he said had been a body-building coach, as an "upstanding and very respectable person" and said he could not imagine what had led him to join Islamic State. Reuters could not verify the authenticity of the post, which was dated Jan. 13.
A Syrian activist who splits his time between Saudi Arabia and Istanbul told Reuters that Fadli had begun fighting two years ago in the Islamist group Ahrar al-Sham, one of several factions battling Syrian government forces, but that like many others he had later left to join the ranks of Islamic State.
Turkish officials said they believed that Fadli had at some stage been captured and tortured, and his toe nails removed, possibly by the Kurdish YPG militia or its political wing, the PYD.
Idris Nassan, a senior official in the Syrian district of Kobani which borders Turkey and is controlled by a majority PYD administration, denied Fadli had ever been held by the group or that there had been any prisoner swaps with Islamic State.
A spokesman for the YPG militia did not immediately respond to a request for comment.
WHO TO BLAME
Turkey sees a multitude of threats from Syria's civil war and is investigating Fadli's potential links to several of them.
A member of the U.S.-led coalition against Islamic State, it was hit by two major bombings last year blamed on the radical Sunni group, in the border town of Suruc in July and in Ankara in October, the latter killing more than 100 people.
But it also sees the YPG and PYD as terrorist groups with close links to the Kurdistan Workers Party (PKK), which has fought for three decades for greater Kurdish autonomy in Turkey's southeast. It fears Kurdish territorial gains in Syria will stoke violent separatist sentiment inside Turkey.
It also sees a threat from forces loyal to President Bashar al-Assad, a former ally whom it now wants to see toppled, and has repeatedly accused him of covertly supporting Islamic State and seeking to destabilize the Turkish border.
The senior security official and a second government source said Turkish intelligence was investigating the possibility that Fadli had been coerced by the PYD or by Syrian intelligence into the Istanbul bombing.
"It is obvious that there is support behind this attack and we're trying to identify it. It could be the PYD or mukhabarat (Syrian secret police)," the government source said, declining to be named because of the sensitivity of the investigations.
Turkey has been accused by Western allies of waking up too late to the threat from Islamic State and allowing foreign fighters to cross its territory and join the group's ranks, an error for which some say it is now paying the price.
It denies the suggestions, pointing to tighter border controls and the rounding up of hundreds of suspects.
After October's bombing in Ankara, for which there has been no claim of responsibility, Turkish leaders also suggested possible Kurdish militant or Syrian intelligence links.
Prime Minister Davutoglu said a day after the Istanbul bombing that Turkish officials suspected "certain powers could be using Daesh", an Arabic term for Islamic State.
"Now all our work is focused on revealing these and other links," the security official said.
(Additional reporting by Katie Paul in Dubai, Angus McDowall in Riyadh, Tom Perry and Mariam Karouny in Beirut, Dasha Afanasieva in Ankara; Writing by Nick Tattersall; editing by Janet McBride)