Nigeria's government has made preventing attacks by armed herdsmen a security priority in Africa's most populous country, a spokesman for the president said on Wednesday in the wake of an attack that may have left up to 50 people dead.

The government led by President Muhammadu Buhari, a former military ruler, is already contending with the militant Boko Haram insurgency in the northeast and a resurgence of pipeline attacks in the oil-rich southern Niger Delta region.

Clashes over land use between the semi-nomadic, cattle-herding Fulani people and more settled communities that practice a mix of farming and cattle rearing, claim hundreds of lives each year, but have increased in frequency in recent months.

Police and local politicians said seven people were killed on Monday when armed herdsmen, suspected to be Fulani, clashed with locals in the southeastern town of Ukpabi Nimbo, in Enugu state. But local media reports suggest up to 50 were killed.

Two witnesses told Reuters more than 20 people were killed and many were injured in the attack which they said involved herdsmen shooting and burning houses.

Buhari's spokesman Garba Shehu said the police and Nigeria's security agencies, acting on a "directive" from the president, were taking "urgent steps to fully investigate the attacks, apprehend the perpetrators and bring them to justice".

"Ending the recent upsurge of attacks on communities by herdsmen reportedly armed with sophisticated weapons is now a priority on the Buhari administration's agenda for enhanced national security," said Shehu.

"The armed forces and police have clear instructions to take all necessary action to stop the carnage," he said, adding that the government was ready to "deploy all required personnel and resources" to remove the threat to national security.

The latest attack took place in the country's southeast, though in the last few years the unrest has been concentrated in Nigeria's middle belt where the country's mostly Christian south and Muslim north meet.

Fulanis are Muslim and the communities with which they are in conflict in central Nigeria tend to be Christian.

Nigeria, which has around 180 inhabitants, is split roughly equally between Christians and Muslims and around 250 different ethnic groups who mostly co-exist peacefully.