Ivory Coast's government announced on Friday clashes between farmers and nomadic herdsmen killed 17 people in northeastern city of Bouna.
It is feared that the death toll may increase, government said.
"During the night of 23-24 March, the situation became very aggravated and at this stage we have 17 people dead," defence ministry official Vincent Toh Bi said on state television.
Besides the dead, 39 people were also injured in the fighting, five of them after security forces intervened, the official said.
Around 900 defence and security personnel were deployed in the town to restore order.
"This is a provisional toll. This is a crisis. We'll have to wait several more hours, or even several days, to have a definitive toll," said Toh Bi.
Violent disputes between nomadic herders and farmers, often over grazing and watering rights, are not uncommon, but such a high death toll is rare.
The farmers complain that their fields are ruined by the passage of herds of cattle.
The country is facing clashes between ex-President Laurent Gbagbo supporters and government forces after former president refused to step down following his loss to Alassane Ouattara in the 2010 presidential vote.
Gbagbo is charged with war crimes and crimes against humanity related to the civil conflict in the country in 2010.
He has denied the charges, as his landmark trial began at the International Criminal Court (ICC).