At least 74 people killed in two separate attacks by armed groups this week, officials say.

Violence has increased in the region in recent years as population growth leads to an expansion of the area dedicated to farming, leaving less land available for open grazing by nomads’ cattle herds.

Benue state police spokesperson Catherine Anene said 28 bodies were recovered at a camp for internally displaced people in Mgban local government area between Friday evening and Saturday morning.

It was not immediately clear what triggered the attack but witnesses said gunmen arrived and started shooting, killing several people.

The attack followed a separate incident in the same state on Wednesday in the remote Umogidi village of Otukpo local government area, when suspected herdsmen killed villagers at a funeral, Bako Eje, the chairman for Otukpo, told the Reuters news agency.

Paul Hemba, a security adviser to the Benue state governor, said 46 bodies were recovered after Wednesday’s attack.

President Muhammadu Buhari in a statement on Saturday condemned “the recent bout of killings in Benue State in which tens of people were killed in Umogidi community” and directed security forces to increase surveillance in affected areas.

Many attacks in remote parts of Nigeria go unreported as thinly stretched security forces often respond late to distress calls by communities.

Benue is one of Nigeria’s Middle Belt states, where the majority Muslim north meets the predominantly Christian south.

Competition over land use is particularly intractable in the Middle Belt, where fault lines between farmers and herders often overlap with ethnic and religious divisions.

Benue has been one of the states hit hardest by years of disputes between nomadic herders and pastoral farmers who blame herdsmen for destroying farmland with their cattle grazing.

Those conflicts have often spiralled into broader criminality and tit-for-tat revenge attacks between informal armed groups established to protect rival communities.

A spokesman for the national herders association this week urged officials not to blame herders for every attack before carrying out proper investigations.

Separately on Saturday, gunmen abducted at least 80 people in Zamfara state, a hot spot for kidnappings for ransom by armed gangs targeting remote villages.