Pedestrians walk along Istiklal street, a major shopping and tourist district, in central Istanbul, Turkey March 20, 2016, a day after a suicide bomb attack.

A Turkish member of ISIS militant group was responsible for Saturday’s suicide bombing in Istanbul that killed three Israelis and an Iranian and wounded dozens of others, Turkey’s interior minister said.

Efkan Ala identified the bomber as a man born in the southern province of Gaziantep, adding that five people had been detained so far in connection with the bombing.

“We have determined that Mehmet Ozturk, born in 1992 in Gaziantep, has carried out the heinous attack on Saturday in Istanbul. It has been established that he is a member of Daesh,” Ala told a news conference broadcast live on television, using an Arabic acronym for ISIS.

Israel has confirmed that three of its citizens died in the blast. Two of them held dual citizenship with the United States. An Iranian was also killed, Turkish officials have said.

Israeli Prime Minister Benjamin Netanyahu has said Israel is trying to determine whether its citizens were deliberately targeted. Eleven of the 36 wounded were Israelis.

Saturday’s attack on Istiklal Street, Istanbul’s most popular shopping district, appeared similar to a January suicide bombing blamed on ISIS that killed at least 12 German tourists in the city’s historic center.

More than 80 people have now been killed in four suicide attacks so far this year in Turkey, a NATO member that faces multiple security threats.

As part of a US-led coalition, it is fighting ISIS in neighboring Syria and Iraq. It is also battling Kurdish militants in its southeast, where a 2-1/2-year ceasefire collapsed last July, triggering the worst violence since the 1990s.

The spate of bombings has raised questions about Turkey’s ability to protect itself from a spillover of both the Syria and Kurdish conflicts.

An offshoot of the militant Kurdistan Workers Party (PKK) claimed responsibility for two recent car bomb attacks in the capital Ankara that killed a total of 66 people. Turkey sees the Kurdish insurgency as fueled by the territorial gains of Kurdish militia fighters in northern Syria.

High alert

Police were questioning the father and brother of the alleged bomber Ozturk and had determined his identity by checking a DNA sample from the blast scene against one taken from his father, security sources said.

Ozturk’s family reported him missing after he went to Istanbul in 2013, the security sources said.

Police were on high alert on Sunday after the previous day’s attack and due to concerns about potential clashes between security forces and Kurdish militants during a spring festival this weekend that is widely celebrated by Kurds.

The United States and some European embassies had warned their citizens to be vigilant before the Newroz celebrations.

A small group of lawmakers from the Peoples’ Democratic Party, the Kurdish-rooted opposition party, were scheduled to walk to Istanbul’s Bakirkoy district for the festivities. Roads in that area were being closed by police for security reasons, Anadolu Agency reported.

Streets across the city, usually bustling with traffic and pedestrians on Sundays, were eerily quiet apart from the sound of police helicopters buzzing overhead. Television footage showed Istiklal Street virtually empty.

Social media sites such as Twitter and Facebook were not readily accessible, local users reported. Authorities have blocked access to such sites after bombings in the past, usually because graphic images have been shared online.

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