Police said two fishermen, both Tausugs, were shot dead by Maranaw snipers while fishing just a kilometer off the coast of Balabagan town.
Dozens of police officers were sent to quell the fighting, which engulfed three barangays.
"A special peacekeeping contingent is now in the area positioned between the two groups," Chief Superintendent Acmad Omar, Autonomous Region in Muslim Mindanao police director, said.
The clashes began Friday when two men, a Tausug and a Maranaw, got into a dispute that turned into a fistfight.
Balabagan municipal administrator Cabilo Ogca stopped the fisticuffs and scheduled a reconciliation meeting.
Both men attended the meeting accompanied by relatives and friends. When the meeting turned into a heated exchange of words, the Tausugs walked out but came back with handguns.
Ogca, a Maranaw, tried to pacify the angry mob and was shot dead along with three of his bodyguards. Other bodyguards returned fire, killing two of the attackers.
The shooting then deteriorated into a tribal war that forced over a hundred families to flee to nearby Parang town in Maguindanao province.
Parang Mayor Vivencio Bataga, who helping manage operations providing relief to the evacuees, said he has asked the Coast Guard to protect boats ferrying evacuees from Balabagan’s Barangay Dapdap, scene of the heaviest fighting.
One evacuee, Sarikin Jailani, a 40-year-old father of five, said Maranaw snipers were firing at boats carrying evacuees.
"I am praying that the emissaries sent by the ARMM government can convince these armed men to just allow the Tausugs to evacuate to safer grounds in the meantime while the tension in Balabagan is high," Bataga said.
Regional governor Parouk Hussin has directed his executive secretary, Hadji Nabil Tan, to form a team of Maranaw and Tausug regional officials that will help police peacefully solve the conflict.