"The number of people killed has exceeded 100 people from those attacks," Mangu district chairman Daput Minister Daniel told AFP.
"Up till now there were reports of attacks and burning of houses in many places within the local government area."
Plateau State security forces said on Thursday that calm had been restored, but local sources said several villages were still struggling with violence and residents were fleeing.
A lawmaker representing Mangu and neighboring Bokkos in the House of Representatives also said around 100 people had been killed and more than a dozen communities ravaged by attacks.
Lawmaker Solomon Maren told AFP on Friday that the situation was now calm but access to some communities was still complicated.
Plateau State government has so far not given any death toll, only saying the violence "left many dead."
The state government convened an emergency meeting over the attacks and said security forces would maintain a presence on the ground to stem further violence, a statement said on Friday.
The National Emergency Management Agency (NEMA) said more than 3,000 people had been displaced and hundreds of houses destroyed.
Police said five people had been arrested.
Violence across Nigeria has been on the rise in the last few weeks after a brief calm period during the February presidential and March state elections.
Last month, gunmen suspected to be Fulani herders have killed 33 people in an attack on a farming village in northwestern Kaduna state, where intercommunal herder-farmer violence is also common.
Nigeria's security forces in the northwest are also battling heavily armed bandit militias, as well as a 14-year-old jihadist insurgency in the northeast and separatist tensions in the southeast.
Your browser doesn’t support HTML5
Thousands Displaced in Central Nigeria After Deadly Clashes