The attack was the deadliest in a series of bombings in Turkey this year. President Tayyip Erdogan described the attack as an attempt by Islamic State extremists to destabilize the country by exploiting ethnic and religious tensions.
"Initial evidence suggests it was a Daesh attack," Erdogan said in Istanbul on Sunday, using an Arabic name for the hardline Sunni Islamist group. He said 69 people were in hospital and 17 were "heavily injured".
Islamic State has been blamed for other similar attacks in Turkey, often targeting Kurdish gatherings in an effort to inflame ethnic tensions. The deadliest was last October, when suicide bombers killed more than 100 people at a rally of pro-Kurdish and labour activists in Ankara.
The pro-Kurdish Peoples' Democratic Party (HDP) said the wedding party was for one of its members. The groom was among those injured, but the bride was not hurt.
The bomb went off as guests spilled out into the streets of the city close to the Syrian border after the traditional henna night party, when guests have their hands and feet painted.
Women and children, including a three-month-old baby, were among the dead, witnesses said. A destroyed suicide vest was found at the blast site, officials said.
Blood and burn marks stained the walls of the narrow lane where the blast hit. Women in white and checkered scarves wept outside the morgue waiting for word on missing relatives.
"The celebrations were coming to an end and there was a big explosion among people dancing," said 25-year-old Veli Can. "There was blood and body parts everywhere.
We want to end these massacres," witness Ibrahim Ozdemir said. "We are in pain, especially the women and children."
Hundreds gathered for funerals on Sunday, with coffins draped in the green of Islam. But some ceremonies would have to wait because many victims were blown to pieces and DNA tests would be needed to identify them, security sources said.
"Every type of death is painful. But it is even more painful when it comes with religious slogans. It is even more painful when they mix religion with politics," said Omer Emlik, who said he was an uncle of two of the victims. All the people here are suffering.More photos from the scene...