Erdogan said Saturday's blast in Gaziantep near the Syria border "was the result of a suicide bomber aged between 12 and 14 who either detonated (the bomb) or others detonated it."
The explosion was the latest attack to rock the key NATO member in a horrific year that has seen strikes blamed on Kurdish and Islamist militants as well as a bloody July 15 botched coup.
The remains of a suicide vest were found at the scene, the chief prosecutor's office said Sunday according to broadcaster CNN-Turk.
Gulser Ates, one of scores wounded in the attack, told Hurriyet the attack took place as the party was breaking up.
"We were sitting on chairs, having a chat with one of our neighbours.
"During the explosion, the neighbour died on top of me. I remember being underneath. If my neighbour hadn't fallen on top of me, I would have died," she said.
"The bride and groom's happiest day was poisoned."
Another resident in Gaziantep told Dogan news agency he saw many dead bodies and body parts including a "head, arm, hand scattered on the ground".
The bride and groom – Besna and Nurettin Akdogan – were rushed to hospital but were not seriously wounded.
According to the state-run Anadolu news agency, the bride was released from hospital, saying as she left: "They turned our wedding into a bloodbath."
Meanwhile, images on broadcaster CNN-Turk showed rows of coffins covered in white sheets.
Crowds of mourners gathered to pray and chants of Allahu Akbar ("God is greatest") could be heard.
'You will not succeed'
Erdogan told reporters the death toll was now 51 with 94 hurt in the attack.
A total of 69 people remained in hospital, with 17 in critical condition.
The bride and groom were reportedly from the mainly Kurdish region of Siirt further to the east and had themselves been uprooted due to the flare-up in violence with Kurdish militants.
The pro-Kurdish Peoples' Democratic Party (HDP) said its members had been present at the wedding, also attended by many women and children.
Erdogan said such attacks aimed to sow division between Turkey's different groups including Arabs, Kurds and Turkmen and to "spread incitement along ethnic and religious lines".
Many extremists see Kurds as one of their main enemies, with Kurdish militias playing a significant role in the fight against Daish on the ground in Syria.
A defiant Erdogan said there was "no difference" between the group of US-based preacher Fethullah Gulen – whom he blames for the failed coup bid – the outlawed Kurdistan Workers Party (PKK) "and Daish (IS), the likely perpetrator of the attack in Gaziantep".
"Our country and our nation have again only one message to those who attack us – you will not succeed!" he said.
Prime Minister Binali Yildirim said Gaziantep would show the same spirit it had shown in 1921, when it defeated French forces in Turkey's Independence War which led to the word Gazi (war hero) being added to its original name of Antep.
"Our grief is great, but be sure our unity and togetherness will defeat all these diabolic attacks," he said.
World leaders quickly condemned the attack, with President Francois Hollande denouncing the "vile" incident and pledging that France "stands with all who fight against the scourge of terrorism."
US ambassador to Turkey John Bass condemned the "barbaric attack on innocent civilians", adding that Washington would "continue to work closely together to defeat the common threat of terrorism."
The pope called on faithful to pray for the victims while Chancellor Angela Merkel condemned the "cowardly and underhand" attack "in the strongest terms."
Hub for Syrians
A major city just 60 kilometres (37 miles) north of the Syrian border, Gaziantep has become a hub for Syrians fleeing the civil war in their country.
But as well as refugees and opposition activists, there have long been fears it was home to a significant militant presence.
Daish suicide bombers have carried out several attacks in Istanbul this year, while Kurdish militants have hit targets in both Ankara and Istanbul.
On Thursday, 12 people were killed in three bombings blamed on the PKK, who Erdogan said had killed 70 members of the security forces in the last month alone.
The blast in Gaziantep came just hours after Yildirim said Ankara would play a "more active" role in efforts to solve the Syrian civil war.
Turkey was long accused of turning a blind eye to or even abetting the rise of Daish in Syria, claims it vehemently denies. But Ankara has taken a tougher line since the start of militant attacks on its soil.
