Istanbul / AFP
Turkish investigators were scrambling on Sunday to identify the bomber who blew himself up in the heart of Istanbul, killing four foreigners in the latest bloodshed to rock the country.
No group has yet claimed responsibility for Saturdayâ€™s blast, which killed three Israelis and an Iranian.
The attack came six days after a suicide car bombing at a busy square in the capital Ankara that killed 35 people and was claimed by Kurdish rebels.
But local media said IS extremists were suspected of being behind the latest attack which targeted Istiklal Caddesi, a bustling pedestrian street in central Istanbul that is lined with shops and cafes.
The suspected bomber was named by pro-government media as Savas Yildiz, a 33-year-old Turkish national.
Dogan news agency said DNA samples had been taken from the suspectâ€™s father to try to obtain a match with the attacker.
But Istanbul governor Vasip Sahin refused to give details on the tests, saying only: â€œOur investigation into this question is continuing.â€
Of the 39 people wounded in the attack, 24 were foreigners. By Sunday morning, 19 people were still being treated in hospital, eight of whom were in critical condition, the health ministry said.
The three Israeli victims, two of whom also held US citizenship, were part of a group which was on a gastronomic tour of Turkey, Israeli media said.
Their bodies were to be repatriated on Sunday aboard an Israeli military jet, according to military sources. Five injured Israelis were flown home for treatment on Saturday night, Israelâ€™s emergency services said.
Turkey has suffered six bombings since July that have killed more than 200 people around the country.
The only attack in Istanbul during that time, outside the Blue Mosque in January, had targeted a tourist quarter.
That suicide bombing, which claimed the lives of 12 German tourists, was blamed on IS.
The extremist group was also held responsible for Turkeyâ€™s worst ever attack, which killed 103 people in October at a rally in support of Kurdsâ€”arch-enemies of IS across the border in Syria.
Yildiz, named as a suspect in Saturdayâ€™s attack in Istanbul, was also suspected of two bombings on offices of the pro-Kurdish Democratic Peoplesâ€™ Party in May 2015 in the southern cities of Adana and Mersin.
â€˜Terrifyingâ€™ new reality
On Sunday morning, the two-kilometre Istiklal Caddesi street and nearby Taksim Square, the cityâ€™s main rallying point, were eerily quiet, reflecting the growing nervousness of Turks over the seemingly indiscriminate nature of the attacks.
â€œYou never know here it can happen. Itâ€™s terrifying,â€ said Ismail, a chef from a restaurant near the scene of Saturdayâ€™s attack.
Prime Minister Ahmet Davutoglu vowed to track down those responsible, while NATO allies the US and Europe said they stood by Turkey.
â€œWe will fight with determination and perseverance until all forms of terrorism are eradicated,â€ Davutoglu said on Saturday.
Turks are reeling from the increased frequency of attacks that risk dealing a knockout blow to the countryâ€™s vital tourism trade.
â€œTourism is over, because of the bombs,â€ Imdat, a disconsolate taxi driver with greying hair and a black leather jacket, told AFP as he waited for customers at a rank in Istanbulâ€™s Beyoglu district.
A Kurdish rebel group, the Kurdistan Freedom Falcons (TAK), had claimed responsibility for the March 13 suicide car bombing on a busy transport hub in Ankara.
TAK, which also claimed a February attack targeting troops in Ankara that killed 29 people, has ties to the outlawed Kurdistan Workersâ€™ Party (PKK) against which the Turkish army is fighting in a major offensive.
In July, the PKK resumed its three-decade-long insurgency for autonomy for the Kurdish minority, following the collapse of a shaky two-year ceasefire.
The conflict, which has been concentrated in the mainly Kurdish southeast of the country, has claimed some 40,000 lives.