The explosion is the latest attack to have rocked the key NATO member in a horrific year that has seen a string of strikes blamed on Kurdish and Islamist militants as well as a bloody July 15 botched coup.
Gaziantep governor Ali Yerlikaya said in a statement that 30 people had been killed and 94 wounded in “an abhorrent terror bomb attack on a wedding”.
A previous toll had put the number of dead at 22.
“We condemn the traitors who organised and carried out this attack,” he said, vowing that those responsible would be “brought to account”.
Mehmet Erdogan, a ruling Justice and Development Party (AKP) lawmaker for Gaziantep said it was not clear who was responsible for the explosion but there was a “high possibility” it was a suicide attack.
The lawmaker added that it was the type of attack that could have been launched by the Islamic State (IS) group or the Kurdistan Workers’ Party (PKK).
The explosion took place in the Sahinbey district of the city which is said to have a large number of Kurdish residents, fuelling speculation of Islamic State (IS) jihadist involvement. Reports said the wedding had a strong Kurdish presence.
“Initial information suggests it is Daesh (IS) who did this,” Gaziantep MP for the AKP, Samil Tayyar, was reported as saying by Dogan news agency.
He added: “It is an area where many of our Kurdish brothers live.”
The pro-Kurdish Peoples’ Democratic Party (HDP) said its members had been present at the wedding which was also attended by many women and children.
“The aim of terror is to scare the people but we will not allow this,” said Deputy Prime Minister Mehmet Simsek, who also represents Gaziantep in the Turkish parliament, adding that a suicide bombing was the likely cause.
A major city lying just 60 kilometres (37 miles) north of the Syrian border, Gaziantep has become a hub for Syrians fleeing the civil war in their country.