He ruled out suggestions that the PKK, a Kurdish separatist group which is active in the area where the attack took place, had been involved.
Blood feuds are frequent in Turkey's Kurdish-populated regions, where feudal traditions are strong.
Local media said the families of both the bride and the groom included members of the Village Guard, a controversial state-backed militia set up to combat Kurdish separatist fighters in southeast Turkey.
Al Jazeera's Anita McNaught, reporting from Istanbul, said: "Even by the standard of Turkey's intermittently violent southeast, this is a massacre of a scale they haven't seen for years if not decades.
"It's a very complex situation. One factor is the blood feud. The other factor I think we have at play is the Village Guard.
"Some of them still do the government's bidding of keeping law and order in the southeast. Others have mutated into in a quasi-mafia organisation. They're heavily armed and to a degree they're running their own affairs.
"Adding to this a toxic mixture of domestic violence and high unemployment, you get the kind of climate which creates the kind of violence we're seeing."
Television broadcasters said there had been a blood feud between two families in the small village in recent years.
'Rifles and hand grenades'
Ahmet Ferhat Ozen, the acting governor of Mardin, told the Reuters news agency that masked men stormed into the hall where wedding guests were assembled and opened fire with automatic rifles and hand grenades.
"There were a few people, they broke into the house and started spraying the place with bullets, hitting both men and women, their faces were covered with masks," a 20-year-old female witness said.
She said there were about 200 people at the gathering.