Lagos - Nigeria's acting president Yemi Osinbajo has ordered troops in to keep the peace in the restive state of Taraba after deadly clashes between herders and farmers.The vice-president, standing in for President Muhammadu Buhari, who is on indefinite medical leave, said on Thursday the extra military battalions and police reinforcements had been sent.Police say 18 people were killed in unrest between the Mambilla and Fulani groups in the central state earlier this week but others put the death toll at more than 100.A local senator put the death toll at about 50 but it was not possible to independently verify that figure."With great sorrow, I offer my condolences to the victims of the violent attacks in communities in Taraba State," Osinbajo said in a statement posted on Twitter on Thursday evening. "The perpetrators of these attacks and acts of violence will be brought to book," he said.When asked about the the death toll and how many troops have been deployed to the area, Nigerian armed forces spokesperson John Enenche said "no confirmation yet".The clashes comes as Osinbajo is trying to keep a lid on simmering ethnic tensions and has been calling for national unity in the face of an upsurge in separatist sentiment across Nigeria. 'Cycle of violence' The Mambilla and Fulani clashed in Ngoroje village and the violence spread to other communities in the state, which borders Cameroon."We have lost 105 herdsmen in the Mambilla crisis in the last five days," said Mohammed Keruwa, head of the Myetti Allah Cattle Breeders' Association of Nigeria, an umbrella Fulani organisation. "So far 40 settlements have been affected with over 100 homes razed. The Mambilla tribes are envious of the Fulani herders, whom they see as taking over their land," he told AFP."The Fulanis are Muslims and the Mambilla tribes are Christian. This adds to the volatility of the situation."Taraba state police spokesperson David Misal added: "The situation is calm now. It was a misunderstanding between two ethnic groups the Mamabilla and the Fulani.Taraba lies in Nigeria's restive "Middle Belt", where the mostly Christian south meets the largely Muslim north, and has long been a flashpoint for ethnic conflict. The wider region is notorious for bloody election campaigns and battles over fertile farmland and resources, with opposing groups often staging brutal tit-for-tat reprisals.Extra troops began arriving in Taraba from Monday, according to Jameel Muhammad, the media aide to Taraba Central Senator Abubakar Yusuf.Political analyst Chris Ngwodo said the state has "very weak security institutions (and) is not able to forcefully confront the incident and punish the perpetrators"."More and more ethnic communities are resorting to self-help and we're seeing a lot of militarisation on the ground, especially in the hinterlands of the country," he added. "This is not the last that we'll see of this particular cycle of violence."