President Buhari has ordered Nigeria's police chief to relocate from the capital Abuja to Benue State, to deal with an upsurge in violence there.
More than 90 people have been killed in Benue and neighbouring Taraba State in the past week.
Eighty-thousand have been displaced by the clashes.
A BBC reporter in Nigeria says the real number of dead is believed to be much higher.
Most of the violence is between nomads and farmers who fight over access to land.
In Nigeria, the Punch news-site is running an online poll asking if Miyetti Allah, the umbrella body of cattle breeders, should be banned after one of its officials defended the New Year killings in central Benue State.
Garus Gololo, who represents the organisation at state level, told BBC Pidgin last week that herdsmen had responded to an attack by "thieves" who had stolen 1,000 cows.
Around 20 people were killed after Fulani herdsmen attacked communities in Guma and Logo area.
However, Othman Ngelzarma, a top official of Miyetti Allah, has condemned the killings in an interview with Channels Television.
He said the attackers are “killers not herdsmen”.
Tensions between Fulani herdsmen and farmers have heightened since Benue state passed an anti-grazing law leaving the herdsmen with nowhere to graze their cows.