The death toll in the attack in the southern city of Gaziantep has now risen to 50, the local governor’s office said, with almost 100 wounded.
A suspected suicide bomber targeted guests at a Kurdish wedding as they danced in the street.
Gaziantep, near the Syrian border, is known to have several IS cells.
The BBC’s Seref Isler, who is from Gaziantep, says the city of 1.5 million was already on edge because of events in Syria, where IS has been battling Syrian Kurdish forces.
A suicide bomber believed to have links to IS killed two policemen in Gaziantep in May.
IS is known to have operatives in Gaziantep.
Turkey has been hit by a series of bombs both by IS and Kurdish militants in the past year. The last IS attack, on Istanbul airport in June, killed more than 40 people.
The jihadists have recently lost ground in northern Syria, including a former stronghold, Manbij. Syrian rebel soldiers are preparing to advance further into the IS-held province of Jarablus.
If this bomb was the work of IS, there will be speculation it was a revenge attack, intended as a show of strength by a group on the defensive.
In a written statement published by local media (in Turkish), Mr. Erdogan argued there was “no difference” between IS, the Kurdish militants of the PKK, and followers of US-based cleric Fethullah Gulen, whom he blames for the coup attempt last month.
“Our country and our nation have again only one message to those who attack us – you will not succeed!” he said.
The bomb went off in a part of town popular with students and which has a large Kurdish community.
Local MP Mahmut Togrul told the Reuters news agency it had been a Kurdish wedding.
Mr. Togrul’s party, the pro-Kurdish Peoples’ Democratic Party (HDP), said the wedding had been for one of its members.