A bomb blast at a wedding party in southeast Turkey killed at least 50 people overnight, Turkish officials said Sunday, in what is now the deadliest in a string of militant attacks in the country this year.

The explosion late Saturday tore through a crowd of revelers at an outdoor marriage ceremony in the city of Gaziantep, roughly 35 miles from the Syrian border, and was blamed on Islamic State militants who operate in the area.

The Turkish president said the suicide bomber was between 12 and 14 years old, the Associated Press reported.

Authorities in Turkey have blamed the Islamic State for at least three attacks in 2016, including a June assault on Istanbul’s Ataturk Airport that left 44 people dead. But the group, which has long used Turkey to access its base in war-torn Syria, has not claimed any of the attacks.

Saturday’s blast would mark the first suspected Islamic State attack in Turkey since the airport assault.

A man is carried as he cries during a funeral for victims of the suspected suicide bombing attack on a wedding party in Gaziantep, Turkey. (Ilyas Akengin/AFP/Getty Images)

“This is a massacre of unprecedented cruelty and barbarism,” Deputy Prime Minister Mehmet Simsek said at the site of attack, the Associated Press reported.

“We . . . are united against all terror organizations,” he said. “They will not yield.”

The pro-Kurdish People’s Democratic Party (HDP) said in a statement that the wedding party had been for one of its members and that “many citizens, including women and children, lost their lives.”

Images from the wedding showed guests wailing as ambulances carried away the dead and wounded. Turkish media reported that the bride and groom were injured but were not in critical condition.

Turkey has been locked in a battle with Kurdish militants in the southeast for more than a year. The government has accused the HDP of supporting Kurdish guerrillas who want more autonomy for ethnic Kurds. The HDP has denies the accusation.

The Kurdistan Workers’ Party — or PKK — is the largest Kurdish militant group and has carried out attacks on Turkish security forces in recent months. The fighting comes after a 2013 peace deal ending decades of conflict fell apart last year.

In addition to clashes between Kurdish and government forces, suicide bombers linked to the Islamic State struck two Kurdish peace rallies in Turkey last year, killing more than 120 people.