Clashes between cattle herders and farmers pose a threat to countries across West Africa and the Sahel, the UN warned on Thursday, after Nigeria's parliament summoned President Muhammadu Buhari over escalating violence.
Lawmakers from Nigeria's lower chamber of parliament, the House of Representatives, called for Buhari to explain what his government was doing to stop increasingly bloody clashes in the country's central region.
On Tuesday, at least 18 people, including two Roman Catholic priests, were killed in an attack on a church near the state capital Makurdi that was blamed on herdsmen.
Eleven ethnic Hausa traders were killed in Makurdi in retaliation, with unconfirmed reports of separate attacks elsewhere in the restive state.
The violence coincided with a meeting of ministers from the West African regional bloc Ecowas to discuss seasonal migration of livestock.
In West Africa and the Sahel, there are more than 60 million cattle, according to Jean-Claude Kassi Brou, the president of the Ecowas Commission.
UN Secretary-General Antonio Guterres' special representative for West Africa and the Sahel, Mohamed Ibn Chambas, said there had been an increase in clashes region wide.
He said in a speech that a resource conflict was being aggravated by rapid population growth, climate change, poor implementation of legislation and the availability of weapons.
Wider criminality was further exacerbating tensions.
"Farmers-herders conflict is the new sub-regional security threat," he said.
"Urgent action is needed to resolve conflict in countries currently experiencing high levels of violence between herders and farmers," he added.
"Sustained conflict prevention efforts are needed to stop violence from taking root and the state needs to be actively involved, working with local communities."
Buhari denounced this week's attacks in Benue state as "evil and satanic", and has previously called for restraint on all sides.
The government's proposal is to create cattle ranches or grazing colonies for herds but that has been fiercely opposed in some states, including in Benue.
Critics of Buhari say he has done little or nothing to stop the violence because the herders are his kinsmen from Nigeria's mainly Muslim north.
The speaker of the House of Representatives, Yakubu Dogara, said late on Wednesday that lawmakers "passed a vote of no confidence on (military) service chiefs and security advisers and called for their replacement".
"We also resolved to summon (Buhari) in order to answer pertinent questions concerning what the Executive is doing to put a decisive end to the spate of killings in different states of the Federation," he wrote in a tweet.
"The foremost responsibility of government is to ensure the safety of lives and property and as a responsive Legislature backed by the mandate of our constituents, we cannot continue to look on as our people are murdered in cold blood."
In Benue state, some 385 people have been killed in clashes since January, according to the US-based Armed Conflict Location and Event Data (ACLED) project.
The state lies in Nigeria's so-called Middle Belt, where the mainly Muslim north meets the predominantly Christian south.
Thousands of people have been killed over decades in clashes between cattle herders and farmers over land and water, with the conflict polarised along religious and ethnic lines.
Local politicians have described the state as "under siege" while Christian groups have expressed fears about Islamification. Cattle breeders say they suspect a political agenda.
Buhari, elected in 2015, has promised to be tough on "insurgency, terrorism, ethnic and religious violence, kidnapping (and) rural banditry".
He is seeking re-election in February next year.
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