There have been six suicide bombings in Turkey in less than a year
The suicide bomber behind Saturday's attack in Istanbul that killed four people has been identified as a member of Islamic State (IS).
Interior Minister Efkan Ala said Mehmet Ozturk, who was born in 1992 in the southern city of Gaziantep, carried out the "heinous attack".
"It has been established that he is a member of Daesh," Mr Ala told a news conference, using an Arabic acronym for the militant group.
He said Ozturk had no criminal record, and added five people have been detained as part of the investigation.
The bombing happened in Istanbul's main shopping street, a thoroughfare on the European side of the city lined with shops, restaurants and foreign consulates.
Three Israelis, two of whom held dual US citizenship, died in the attack, along with an Iranian.
The Israelis have been identified as Avraham Goldman, 69, from Herzliya, Simha Damari, 60, from Dimona and Yonata Shor, 40, from Tel Aviv.
It was not immediately clear if the Israelis were specifically targeted.
Another 36 people were wounded, seven of them seriously.
There have been six suicide bombings in Turkey in less than a year.
The country is confronting a wide range of security threats, including from ultra-left radicals, Kurdish rebels demanding increased autonomy and IS militants.
Turkey is a partner in the US-led coalition against the terrorist group, and its air bases are being used to launch bombing raids against the IS in neighbouring Syria.
Mr Ala said Turkey was determined to press ahead in its battle against terror groups, but admitted it was difficult to prevent suicide attacks.
There is heightened security across the country in the run-up to the Kurdish spring festival of Newroz on Monday, which Kurds in Turkey traditionally use to assert their ethnic identity and demand greater rights.
Mr Ala said 120,000 police and 80,000 military police were on duty during Newroz and more than 1,000 police checkpoints have been set up.
People on Sunday placed flowers and candles at the scene of the attack, with one placard reading "We are on the streets, we are not afraid of you."