At least 51 persons have been killed by an airstrike in the Rukubi community, Ekye Development Area of Nasarawa State.
A bomb was dropped on them by an unidentified helicopter.
The area, which is in Doma Local Government Area, shares a border with Benue State.
A mass burial was held in the council.
Police spokesman, Ramhan Nansel, said he could not confirm the number of casualties.
He said the state police command was working with sister agencies to arrest the perpetrators.
Nansel said: “It is unfortunate that such a thing happened.
“The police and other security agencies are working round the clock to understand what led to the attack and track down those involved in the act.”
Governor Abdullahi Sule said he was in touch with his Benue counterpart, Samuel Ortom, to bring the situation under control.
He said the incident led to the death of many pastoralists, promising to ensure that those behind the killings are apprehended.
The governor urged herdsmen to remain calm, saying the state government was liaising with Benue to find a lasting solution to the incessant attacks along the Nasarawa/Benue border.
He added that security operatives have been deployed to curtail any further breakdown of law and order in the area.
Sule said: “On behalf of the state government, I want to sympathize with the people across the state over the killings by an unknown bomber.
“I want to assure them of the state government’s commitment to unraveling the perpetrators to ensure they face the full wrath of the law.”
Chairman of Doma LGA, Ahmed Sarki-Usman, praised the pastoralists for being calm and allowing the government and security agencies to handle the issue.
“I assure them that we will get to the root of the matter,” he said.
The State Chairman, Miyetti Allah Kautal Horai, Ardo Lawal Dano, expressed shock over the bombing that killed his kinsmen.
He appealed to the federal and state governments to come to their aid to arrest those involved in the act.
Dano said: “We are law-abiding citizens. We don’t like trouble, so let the government address the situation because we are really pained losing our loved ones.”