Pressure is growing on Nigeria's President Muhammadu Buhari after a spate of killings of Christians in the country's Middle Belt region.

Herdsmen from the nomadic Fulani ethnic group, who are Muslims, have been targetting Christians, who are mainly agriculturalists. While there have been long-standing tensions between the two groups, herdsmen are now armed with weaponry including AK47 assault rifles and critics say they have been infiltrated by Islamist terrorists.

In a meeting yesterday with Buhari, US president Donald Trump took the Nigerian president to task for not doing more to stem the violence. In a joint press conference he said: 'We are deeply concerned by religious violence in Nigeria including the burning of churches and the killing and persecution of Christians. It's a horrible story.'

He said: 'We encourage Nigeria and the federal state and local leaders to do everything in their power to immediately secure the affected communities and to protect innocent civilians of all faiths including Muslims and including Christians.'

The Fulani attacks are now claiming more lives than the better-known Boko Haram insurgents in the north east of the country. Hundreds of Christians have died this year, including two attacks last week that claimed 19 and 39 lives respectively.

Nigeria's House of Representatives summoned Buhari to appear and account for the killings. It also passed a vote of no confidence in the country's armed forces chiefs and the security advisers to the president, and suspended its sittings for three days.

Church leaders have condemned the government's failure to deal with the situation. A statement from Nigeria's Catholic Bishops Conference entitled 'When Will This Barbarism End?' after the killings of two priests and their parishioners said Christians feel 'totally exposed and most vulnerable'. It said bishops had repeatedly raised the issue of security and felt 'violated and betrayed' at the lack of action.

The statement called for Buhari to resign, saying: 'Whether this failue is due to inability to perform or lack of political will, it is time for him to choose the part of honour and consider stepping aside to save the nation from total collapse.' It also called on Nigerians to arm themselves for self-defence.

The Methodist Church Nigeria called on Buhari to declare the armed herdsmen terrorists, saying they had 'graduated from carrying bows and arrows to sophisticated weapons, including AK-47 assault rifles which they deploy against host communities across the country'.

Protests by thousands of Christians took place across the country on Sunday led by the Christian Association of Nigeria (CAN). In Ondo state, Rev John Ayo Oladapo said the protest was necessary because of the killing of innocent Christians. 'We are here today to register our displeasure to the on going killings across the country. We want to say Christians in the country are not second class citizens. We will not allow these killings,' he told Vanguard.

Dr Supo Ayokunle, protesting at Oritamefa Baptist Church, Ibadan, said: 'Since 2009, bloodshed has continued, governments after governments, administrations after administrations have been promising us not to fear and go about our businesses, that they are on top of the situation but we have seen that they are never on top of it.'

Buhari, 75, has suffered from poor health but has announced he is to seek another term in office. The continuing violence is expected to impact on his support at the polls.