The latest blast in Turkey, that took place in Istanbul’s historic Sultanahmet Square on Tuesday - a major tourist hotspot - killed 11 and wounded at least 15.
The attack is likely to increase pressure on Ankara to bolster its efforts against terrorism, as well as border controls to stem infiltration.
The suicide bomber was identified by Turkish officials as 28-year-old Nabil Fadli, a Saudi-born man of Syrian origin who was confirmed to be a member of the Islamic State of Iraq and Syria (ISIS).
Turkish Deputy Prime Minister Numan Kurtulmus said: “The blast is an extension of proxy wars that have been going on in Syria over the last five years.”
Experts told Al Arabiya News that the attack was a message to the anti-ISIS coalition that the group was willing to kill people in the heart of a metropolis.
The blast was the latest in a series in Turkey, which suffered two major bomb attacks last year by ISIS that killed more than 130 people in total.
Last year, the Sultanahmet district suffered a suicide bombing by a female from the Russian region of Dagestan with suspected links to Islamist militant groups. She blew herself up at a police station, killing one officer.
ISIS, which publishes an online propaganda magazine in Turkish called Konstantiniyye, the Ottoman name given to Istanbul, is believed to have about 50 sleeper cells in the city. After the Sultanahmet attack, several ISIS suspects were detained.
“The location of the attack was Sultanahmet, but those targeted were mostly Germans. [ISIS] surely conducted prior exploration of the scene and chose the German tourist group on purpose,” Metin Gurcan, a security analyst and former special-forces officer, told Al Arabiya News.
He said Germans may have been targeted because of their country’s involvement in the anti-ISIS coalition in Syria and Iraq.
“Expanding the military front to soft targets such as tourists underscores ISIS’s primary aim, which is expansion on various fronts at the same time,” Gurcan added.
He said Turkish authorities had “a delayed response in revealing information about the attack, and attempted to keep them low profile, as was seen during the Ankara attack in October.”
Experts say after the Istanbul attack, there will be greater international pressure on Turkey to do more against ISIS.
However, “Turkey is fighting terrorism on two fronts, against ISIS and against the Kurdistan Workers’ Party [PKK],” Gurcan said, adding that the toughest question is which should be Ankara’s primary target.
He said there should be a comprehensive strategy against sleeper cells of extremist groups in the country, a program to raise public awareness, tougher operational procedures for security officials to track down terrorists, and political assertiveness.
Canalp Korkmaz, a PhD candidate in security strategies at the Turkish National Police Academy, said one of the main motivations of the attackers was to portray Turkey as insecure.
“Attacking a place like Sultanahmet gives the impression that it was not chosen by coincidence,” Korkmaz told Al Arabiya News.
“We have to remember how well organized the Paris attacks were. With suicide attacks, choosing a target is an important factor in spreading terror.”
Korkmaz said ISIS might also have tried to avenge the recent killing of 17 of its fighters by Turkish soldiers.