Five people, including a suicide bomber, were killed and 39 wounded in a suspected attack by Kurdish militants on a major shopping and tourist district in central Istanbul on Saturday.
The fourth suicide bombing in Turkey this year hit part of Istiklal Street, a long pedestrian zone lined with global brand name shops and foreign consulates, just a few hundred meters from an area where police buses are usually parked.
Preliminary findings indicate that the outlawed Kurdistan Workers Party (PKK) or an affiliate carried out the attack, a senior Turkish official told Reuters.
"The attacker detonated the bomb before reaching the targeted point because they were scared of the police," the official said, adding the bomber had planned to hit a more crowded spot.
All of the dead victims were foreigners: three from Israel and one from Iran, according to Turkey's Health Ministry. The nationality of the bomber was not immediately released.
Most of the wounded, meanwhile, were also foreigners. A spokesman for the Israeli Foreign Ministry said 10 Israelis were wounded and at least 10 were still missing.
Armed police sealed off the shopping street where half a dozen ambulances had gathered. Forensic teams in white suits scoured the area for evidence. Police helicopters buzzed overhead and panicked shoppers fled the area, ducking down narrow sidestreets.
"My local shopkeeper told me someone had blown himself up and I walked toward the end of the street," one neighborhood resident told Reuters.
"I saw a body on the street. No one was treating him but then I saw someone who appeared to be a regular citizen trying to do something to the body. That was enough for me and I turned and went back."
Turkish Prime Minister Ahmet Davutoglu denounced the suicide bombing as "inhumane" and said Turkey would continue its struggle against "centers of terrorism."
"No center of terrorism will reach its aim with such monstrous attacks," he said in a written statement. "Our struggle will continue with the same resolution and determination until terrorism ends completely."
Istiklal Street, usually thronged with shoppers on weekends, was quieter than normal before the blast as more people are staying home after a series of deadly bombings.
Health Minister Mehmet Muezzinoglu confirmed that at least 39 people had been wounded and seven of those were in serious condition. Twenty-four of the wounded were foreigners, he said, including six from Israel, two from Ireland, and one each from Germany, Iran and the United Arab Emirates.
Ireland's Minister for Foreign Affairs and Trade said in a statement that "a number of" Irish citizens were injured, and he is "deeply saddened by today's horrific bomb attack."
An Israeli government official told NBC News that Prime Minister Benjamin Netanyahu has been updated on the situation, and that he "has instructed that all (Israelis) wounded be returned to Israel."
Saturday's blast was the latest in a series of deadly threats.
A suicide car bombing in the capital Ankara killed 37 people this month. A similar bombing in Ankara last month killed 29 people. A Kurdish militant group has claimed responsibility for both of those bombings.
In January, a suicide bomber killed around 10 people, most of them German tourists, in Istanbul's historic heart, an attack the government blamed on Islamic State.
NATO member Turkey faces multiple security threats. As part of a U.S.-led coalition, it is fighting Islamic State in neighboring Syria and Iraq. It is also battling PKK militants in its southeast, where a 2-1/2-year ceasefire collapsed last July, triggering the worst violence since the 1990s.
The U.S. condemned the latest violence in Istanbul in a statement Saturday, saying the nation "stands in solidarity with our NATO Ally Turkey in combating the common threat of terrorism."
Paul Goldman also contributed to this report.
This article originally appeared on NBCNews.com.