The suicide bomber responsible for the attack in Istanbul on Saturday was identified as a Turkish-born man affiliated with the Islamic State (IS, formerly ISIS/ISIL) terrorist group, the Turkish interior minister has said.

The bomber was born in 1992 in the southern city of Gaziantep, Efkan Ala told the media on Sunday. He was identified by his DNA as Mehmet Öztürk and had no previous criminal record.

He said five people have been arrested in connection with the bombing, which killed four people and injured over 30.

“We have determined that Mehmet Ozturk, born in 1992 in Gaziantep, carried out the heinous attack on Saturday in Istanbul. It has been established that he is a member of Daesh,” Efkan Ala told the media, referring to the IS by its derogatory Arabic acronym.

Earlier Turkish media said the Istanbul bomber had been flagged by the intelligence services as an IS affiliate. The investigator reportedly linked the bomber to his residence in Gaziantep by tracing his mobile phone signal.

The blast happened on Istiklal Street in a popular shopping area of Istanbul. Two Israeli Americans, an Israeli and an Iranian were among the victims. Nobody immediately claimed responsibility for the attack, so some Turkish officials speculated that Kurdish militants rather than IS terrorists may be behind it. The bombing was the fourth such attack this year, with two of them claimed by a Kurdish militant group.

The bombing happened just ahead of the Newroz celebrations, which are celebrated by many Kurds and occasionally result in clashes between them and Turkish security troops.

In the wake of the bombing and amid the continued crackdown in Kurdish southeast, Turkish police maintained a heavy presence on Sunday. The government also restricted access to social media in an apparent bid to prevent circulation of graphic images of the bombing and other information.