ISTANBUL • Turkey risks facing a new level of threat on its own soil from ISIS after the Istanbul nightclub attack, with the group openly targeting the country as Ankara battles the militants inside Syria.

While the Islamic State in Iraq and Syria (ISIS) had been blamed for several attacks in Turkey over the past year, the brutal gun attack on the Reina nightclub 75 minutes into 2017 was distinctive in its choice of target and by the clear claim issued by the group.

"(ISIS) has clearly decided to target Turkey," said Mr Sinan Ulgen, chairman of the Centre for Economics and Foreign Policy Studies and visiting scholar at Carnegie Europe.

"All the stages have been passed and battle commenced."

The nightclub attack that killed 39 people struck at a symbol of the overwhelmingly Muslim country's secular society, where the Istanbul elite like to party, dance and drink.

It took place in the district of Ortakoy, a traditionally mixed area which, to this day, has working churches and a synagogue.

The attack also came in the early hours of the New Year, as calculated by the Gregorian calendar, which conservative hardliners in Turkey say should not be celebrated at all.

Mr Ozgur Unluhisarcikli, Ankara office director of the German Marshall Fund of the United States, said the attack had sought "to drive another wedge between Turks with secular and conservative lifestyles".

But the attack was also unique in that it was claimed by ISIS in a formal statement - the first time the group has made a clear and undisputed boast of a major strike in Turkey, despite being blamed on several occasions.

"I think they are trying to make it look like something which is unambiguously centrally directed, rather than one just carried out by a supporter," said Mr Charlie Winter, senior fellow at the International Centre for the Study of Radicalisation and Political Violence at King's College in London.

He said that in the past months Turkey has been firmly in the sights of ISIS extremists perhaps more than any other country, with threats repeatedly printed in its so-called magazine Dabiq.

The attack came with Turkey deeply entrenched in a military campaign inside Syria aimed at ousting ISIS and Kurdish militia from the border area. The operation, which has already lasted four months, has transformed the equation in Ankara's approach to the group, making Turkish President Recep Tayyip Erdogan an arch-foe of ISIS.

"The situation changed with the decision by Ankara to launch a military campaign against (ISIS)," said Mr Ulgen.

After a rapid start to Turkey's Syria operation, progress has stalled at the ISIS-held town of Al-Bab, where the Turkish army has suffered its heaviest casualties.

ISIS last month published a video purportedly showing the burning to death of two Turkish soldiers captured in Syria.

Ankara has said three soldiers are being held in Syria, but warned that there is no evidence to confirm the authenticity of the video.

Apart from ISIS, Turkey is also fighting Kurdish militants, who claimed a double bombing in Istanbul that killed 44 after a football match on Dec 10.

"There is no magic wand or quick fix to Turkey's terrorism problem," said Mr Unluhisarcikli. "The ISIS threat in Turkey is not only a spillover of the Syrian civil war, but also a reflection of the radicalisation within Turkey and polarisation."

AGENCE FRANCE-PRESSE