Nigeria's President Muhammadu Buhari is under increasing pressure to sack his security chiefs because of mounting violence that has killed nearly 2 000 people so far this year.The 75-year-old former military ruler was elected in 2015 after pledging to defeat Boko Haram Islamists whose insurgency has devastated the country's remote northeast since 2009.But despite gains against the jihadists, unrest has intensified elsewhere, including a resurgence of deadly communal clashes between farmers and herders, kidnapping for ransom and banditry.Last week, Amnesty International said 1 813 people have been killed in 17 of Nigeria's 36 states since the start of the year - more than double the 894 killed in the whole of 2017.On June 23, more than 200 people from Christian farming communities were killed in the central state of Plateau, renewing calls for more to be done to stem the bloodshed."The authorities have a responsibility to protect lives and properties but they are clearly not doing enough going by what is happening," said the group's Nigeria director, Osai Ojigho.ImpunityEven before the killings in Plateau, lawmakers called on Buhari to improve security, castigating him for failing to protect lives and property.The National Assembly said it would "not hesitate to (invoke) its constitutional powers if nothing is done" in a thinly veiled threat of impeachment.Last week, Buhari met the speakers of the Senate and House of Representatives and indicated an overhaul of the security apparatus could be in the offing.To be sure, Nigeria's military is overstretched by the Boko Haram conflict, which is now in its ninth year, and the sheer number of operations to maintain a fragile peace countrywide.But as well as charges of ineffectiveness, police and top military brass have also been accused of being the executive's placemen to target perceived political opponents.Meanwhile, former chief of army staff and defence minister Theophilus Danjuma rattled the government by calling for people in northern states to take up arms to protect themselves. The government dismissed his suggestion as an "invitation to anarchy". But it has reinforced the perception of systemic state failings.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook"The president has to sack the service chiefs immediately. Nigeria needs fresh blood because those at the helm have failed," said security analyst Don Okereke."It's embarrassing to continue to keep them in office if they are not performing," the former Nigerian Army officer told AFP. Inspector General of Police Ibrahim Idris in particular has been a target for criticism, defying orders to relocate to central Benue state after scores of people were killed."The man is still occupying his position without any consequence. This kind of behaviour and impunity can only happen in Nigeria," said Okereke. "Nigeria is bleeding and nothing concrete is being done to arrest the situation. The security chiefs have to go." The heads of the army, navy, air force and chief of defence staff were initially appointed in July 2015 but had their tenures extended in December 2017. "Buhari should inject fresh blood and let's see if there won't be results," said Okereke.Identity politicsUnderlying the question about the effectiveness of those in charge of keeping civilians safe is identity politics, which is never far from the surface in Nigeria.Nigeria, which is home to more than 180 million people, is almost evenly split between a largely Muslim north and predominantly Christian south. Even before his election, Buhari's opponents warned he had an agenda to "Islamise" Nigeria: the claim is being aired again as he looks towards re-election in February next year.Since coming to power he has been criticised for surrounding himself with a close-knit circle or "cabal" of Hausa-speaking northern Muslims.Critics say he has been slow to act against the ethnic Fulani Muslim cattle herders because they are his kinsmen. He rejects the charge as an "injustice".Taken with the religious dimension to the farmer-herders dispute, that has only reinforced the feeling among Christians that they are being marginalised.Yinka Odumakin, from the Afenifere socio-cultural group representing the Yoruba of the southwest, said: "Of the 17 top security chiefs, 15 of them are from a section of the country."This is not fair in a multi-ethnic nation like Nigeria." "Now is the time to correct this anomaly by replacing the service chiefs to reflect the principle of federal character as enshrined in the constitution."