The President of Nigeria Muhammadu Buhari has ordered an investigation after armed herdsmen attacked farmers, leaving hundreds dead and thousands more displaced.

The Fulani herdsmen armed with guns and machetes attacked the mainly-Christian farmers in the central Benue state in the latest assault in their long-running battle over grazing rights.

Christian Solidarity Worldwide (CSW) reported that the herders, who had the support of a helicpopter, launched their attack on the Agatu Local Government Area of Benue State over several days, displacing farmers and others from at least 25 communities. Varying reports put deaths at 100 to more than 300. There were also reports of at least six villages razed and corpses littering abandoned communities.

There have been regular attacks by Fulani militia and herdsmen, who are mostly Muslim, on farmers in the central states of Nigeria. The attacks are becoming more frequent. The central states are where the mainly Christian south meets the mainly Muslim north.

In 2014 the herders murdered more people than the Somali terror group al-Shabaab, rendering them the fourth most deadly terrorist outfit in the world, according to the Institute for Economics and Peace's Global Terrorism Index.

The new attacks came after the electoral re-run. A few days ago, the herders were driven from six communities they had occupied on the banks of the Benue River. "Violence attributed to armed herders is increasingly becoming an issue in the south of the country," said CSW.

In January, the body of Obi Edward Akaeze Ofulue II, traditional ruler of Ubulu-Uku Kingdom in Delta State, was discovered in the bush in Ekpon, Edo State, days after his kidnap for ransom by Fulanis.

A few days ago, six traditional rulers accused armed herders of destroying local farmlands and raping women in their area. 

Mervyn Thomas, Chief Executive of CSW, said the organisation "welcomes the deployment of troops to Agatu and news of a government investigation into the violence in Benue State and the pledge to tackle the root causes of the violence.

"However, given the scope of herder attacks and the fact that the herders have long constituted a threat to national security, the investigation must be widened to include every area in the country where such violence is occurring," he said.

"It is essential that the government follows through on its promise and that those responsible for the bloodshed in Benue and elsewhere are held to account. The statistics are sobering; a holistic plan to tackle terrorism in Nigeria must address the Fulani herders as well as Boko Haram."