Nigerian authorities on Sunday imposed a curfew in parts of central Plateau state, a day after a suspected Christian militia attacked a convoy of 90 Muslims, killing at least 23.
Northwest and central Nigeria have for years struggled with violence between mainly Muslim nomadic herders and Christian farmers over control of resources, water and land.
Condemning the attack, President Muhammadu Buhari said in a statement that this was "not an agriculturalist-on-pastoralist confrontation -– but rather a direct, brazen and wickedly motivated attack."
On Saturday, "a group of attackers suspected to be Irigwe youths (predominantly Christian)… attacked a convoy of five buses with Muslim faithful," said police spokesman Ubah Ogaba.
A group representing Irigwe people rejected responsibility.
"While we still mourn and grieve, we kindly ask the police command to withdraw such an unfounded statement that is capable of tarnishing and ruining the image of Rigwe people," said Davidson Malison, a spokesman for the Irigwe Development Association.
Police had initially said 22 of the 90 travellers were killed, but the death toll was revised upwards on Sunday.
"Twenty-three of those attacked lost their lives and 23 persons sustained injuries," state governor Simon Lalong said in a statement.
Concerned about "persisting tensions and reported attempts by some persons to take the laws into their hands," the governor "directed the imposition of a curfew on Jos North, Bassa and Jos South," between 6 pm and 6 am.
Later on Sunday, the state government announced a full lockdown on Jos North.
"Hours after announcing a dusk to dawn curfew… Governor Simon Bako Lalong has directed the imposition of a 24-hour curfew in Jos North to contain further security threats," government spokesman Makut Simon Macham said in a statement.
Police said 20 suspects have been arrested while 33 victims have been rescued.
One of the members of the convoy who escaped, Muhammad Ibrahim, said the assault happened along Rukuba road, on the outskirts of Jos, the capital of Plateau state.
The Muslims were returning from Bauchi State, he said, after attending an event to celebrate the Islamic New Year.
"Iregwe militias attacked and used machetes, knives and stones to kill them," said Malam Nura Abdullahi, representative of a local group representing herders, the Miyetti Allah Cattle Breeders Association of Nigeria.
A Muslim leader at the hospital on Sunday said that two more people had died from their injuries.
"On Saturday, we have buried 25 persons, and today two others have died, making a total of 27," said Malam Sabo Umar of the Fityanul Islam of Nigeria group.
For years, Jos was a flashpoint for ethnic strife pitting Christian and Muslim youths against each other.
In September 2001, Christian-Muslim clashes around Jos left 913 people dead, according to Human Rights Watch.
While the governor said the attack on Saturday "should not be given any ethnic or religious colouration," the presidency described it as a "pre-arranged assault on a known target, location and religious persuasion of the travellers, not an opportunist ambush."
"These kinds of attacks on our country's citizens are unacceptable, heinous, and stand in complete contradiction to the teachings of the great religions of our nation," the presidency added.
Violence in central Nigeria is just one of the challenges facing Africa's most populous country.
Security forces are also battling a 12-year jihadist insurgency in the northeast, kidnap gangs in the northwest and separatist agitation in the southeast.