BAUCHI, Nigeria (Reuters) - More than 20 people have died in clashes between herders and farmers in central Nigeria, police said, part of an outbreak of violence that has piled pressure on President Muhammadu Buhari less than a year before elections.

Two herders went missing in the central state of Benue on Monday and one was later found dead, a state police spokesman said.

In revenge, a group armed with machetes attacked people, including women and children, in the district of Okpokwu the same day, the spokesman said. Twenty-four people died in that violence, he added.

“Four suspects have so far been arrested in connection with the gruesome murder,” the spokesman said.

Some opposition politicians have accused Buhari of failing to take action against the herders because they are his ethnic and religious kin - an accusation his supporters dismiss.

The herders are mostly Muslims from Buhari’s Fulani ethnic group, while the majority of the farmers are Christians of other ethnicities.

Many of the clashes between the communities, triggered by competition over dwindling arable land, have become part of a cycle of revenge attacks that shows little sign of abating.

The presidency said Buhari would begin a tour of areas hit by the clashes, including Benue, on Monday. [nL5N1QN2YL]