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ISTANBUL—Turkey's president blamed Islamic State for turning a youth into a human bomb at a crowded outdoor wedding party in southeast Turkey's largest city, killing at least 51 people in a weekend attack that underscored how the war in neighboring Syria is destabilizing the region.

The bombing in Gaziantep targeted a largely Kurdish neighborhood and turned a celebratory summer evening into a scene of anguish and mourning, as the couple recovered on Sunday from injuries sustained in the massive Saturday blast and investigators worked to identify the charred body parts of guests and family members.

Dozens of funerals took place on Sunday, including ceremonies for 29 children who forensics teams had managed to identify. Nearly 100 people, including many women and children, were wounded in the attack.

There was no immediate claim of responsibility, but President Recep Tayyip Erdogan said a youth between the ages of 12 and 14 carried out the attack and said the bombing had the hallmarks of Islamic State.

Turkey has been battling the terror group as part of the international coalition, and has suffered multiple bombings targeting Turkish citizens already this year, including a devastating attack at Istanbul's Atatü rk International Airport.

Turkey's Kurds in particular have come under fire from Islamic State. Kurds in Syria and Iraq, who are ethnically related to their kin in Turkey, have been among the most active groups fighting the extremists. Previously, Islamic State bombed a Kurdish rally in the Turkish capital and killed more than 100 people last year.

Earlier this month, a Syrian rebel offensive carried out largely by Syrian Kurdish groups and backed by U.S. special operations forces routed Islamic State positions in the Syrian city of Manbij, cutting the terror group's last major road link to Turkey, which it had used to shuttle foreign fighters and supplies to its so-called caliphate. Turkey's prime minister said Saturday that his nation was stepping up its role in finding a peace deal for Syria.

The attack on the wedding party came just before 11 p.m. on Saturday. Besna and Nurettin Akdogan were presiding over traditional henna ceremonies ahead of their formal wedding day. Friends and relatives were outside to enjoy the festivities in the neighborhood, home to many families who had fled violence between the Kurdistan Workers' Party, or PKK, and government forces across Turkey's southeast to the relative peace of Gaziantep.

Witnesses told Turkish television that guests had been dancing and enjoying themselves when the explosion, which was loud enough to be heard several neighborhoods away, tore into those celebrating.

Those who survived, or who rushed to the scene to help the injured, were overwhelmed with gruesome scenes. "We couldn't see anything. Nothing but body parts," the groom's brother, Sukru Akdogan, told the state-run Anadolu news agency.

Besna Akdoğan was discharged from the hospital on Sunday, but needed assistance from her relatives to make it home. "They turned our wedding into blood," she said, according to Anadolu.

Hospital workers had identified only 41 of those killed by Sunday night, among them a three-month-old baby and a Syrian boy.

It is unclear how the attacker penetrated the event. President Erdogan also said it was unclear whether the suspected young bomber triggered the explosives on his own, or whether they were detonated remotely. The local prosecutor's office said it had recovered fragments from a possible suicide vest, and in a statement said that more information would be released about the identity of the attacker in due time.

Since Turkey joined the coalition against Islamic State in August 2015, the terror group has targeted its citizens in several major attacks. The group has branded Turkey an infidel Muslim nation and hostile regime.

Islamic State operatives have long used Gaziantep, which is located only 70 miles from Aleppo, to hunt Syrian opposition figures and journalists who fled the fighting in their homeland and gained refugee status in Turkey.

In April, Islamic State claimed responsibility for an attack in which one of its operatives shot a Syrian opposition journalist in the head while he was walking in an outdoor market in the Turkish city. Another Syrian journalist was assassinated there in December.

These attacks on Kurds have soured the already checkered relationship between Turkey's major opposition party, the People's Democratic Party, or HDP, and the ruling Justice and Development Party, or AKP.

The HDP, which represents a significant segment of the minority Kurdish population, has accused the government of playing down the threat from Islamic State to its constituents, who largely live in the southeastern areas near the Syrian border where Islamic State cells operate.

The government denies those allegations and says it is committed to keeping all of is citizens safe from terror. During the first five months of 2016, 989 individuals in Turkey were detained on suspicion of having links to Islamic State, according to government statistics. A total of 228 of those remain behind bars. The numbers weren't broken down by national origin of the detainees.

Western allies also complain that Turkey isn't using its limited security and intelligence resources in the most effective way to battle Islamic State. Turkey says that it has three urgent counterterrorism priorities: Islamic State, Kurdish militants, and sympathizers with Fethullah Gulen, the U.S.-based Turkish religious leader who the government accuses of masterminding July's failed coup attempt. Mr. Gulen denies being behind the plot.

The wedding attack sparked an outpouring of sympathy in America and Europe, where ties with Ankara have fallen to a recent low after Turkish officials criticized what they call a lack of empathy from Brussels over the failed coup.

The U.S., French and German governments, as well as the European Union, all condemned the attack and sent condolences.

Russian President Vladimir Putin also expressed solidarity with Mr. Erdogan, in a move likely to help consolidate improving ties between Ankara and Moscow. Relations between the countries had been strained since last November, when Turkish jet fighters downed a Russian warplane last year near the border.

Valentina Pop in Brussels contributed to this article.

Write to Margaret Coker at margaret.coker@wsj.com and Thomas Grove at thomas.grove@wsj.com

(END) Dow Jones Newswires

August 21, 2016 21:55 ET (01:55 GMT)

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