The governor of a Nigerian state badly hit by violence between farmers and herders has quit President Muhammadu Buhari's ruling party, after a wave of defections by lawmakers.Samuel Ortom was elected as governor of Benue in 2015 for the All Progressives Congress (APC) party but has been openly critical of the government's response to the deadly clashes.The International Crisis Group said in a report Thursday that more than 1 300 people had been killed in the violence across central states since January this year.Ortom announced late on Wednesday that he was moving back to the main opposition Peoples Democratic Party (PDP) after "due consultations with relevant stakeholders"."I have resolved that the way forward is to rejoin (the) PDP," he added.Ortom's move comes after dozens of lawmakers in parliament in Abuja on Tuesday dumped the APC for the PDP in a sign of growing discontent at Buhari's leadership as elections approach.Buhari, 75, is seeking a second, four-year term of office in February next year, despite claims he is too old and questions about his health following a lengthy, undisclosed illness.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. The former military ruler has also been criticised for his handling of rising violence as well as the alleged used of security services to target his perceived political opponents.Ortom has been one of the most vocal opponents of Buhari's response to the resource conflict, which has become polarised along ethnic, political and religious lines. The governor's ethnic Tiv kinsmen, who are Christian, have been targeted. The herders are mainly ethnic Fulani Muslims, as is Buhari.APC flags have now been removed from public places in Benue, according to an AFP reporter in the state.The ruling party said it was "somewhat surprising" Ortom had left and it was still working to try to reconcile disgruntled members."Even with this development, we don't think it is too late for reconciliation," it said in a statement.He met APC senators in Abuja late on Wednesday as part of efforts to broker a truce in the party, which last month saw a splinter group emerge of disaffected members.