The international community must act after at least 140 Christian school children were kidnapped in Nigeria on Monday, Release International has said.
The children were taken by gunmen from Bethel Baptist boarding school in Kaduna at 2am on Monday morning.
The gunmen, suspected to be Fulani militants, forced their way into the school after overpowering security guards.
The abducted children account for most of the students in attendance at the 180-strong school.
Paul Robinson, the CEO of UK-based Release International, which supports persecuted Christians around the world, said the kidnapping of the children amounts to an "appalling failure by Nigeria to protect its Christian citizens".
"Our hearts and prayers go out for these kidnapped children and their parents. God knows what they are going through," he said.
While some observers have blamed Fulani violence against Christians on a farmer/herder conflict, Robinson said this would be "a gross over-simplification".
He called on the international community to compel Nigeria to take effective action to protect the country's persecuted Christian minority, which has come under repeated attack by radicals in the north.
In addition to radicalised Fulani, Christians are experiencing attacks by members of militant groups like Boko Haram and ISWAP (Islamic State West African Province).
"By attacking Christians in the north and middle belts of Nigeria, the Fulani militants are serving the same jihadist agenda as these Islamist terror groups,' Robinson said.
"And the Nigerian government is simply not doing enough to protect its Christian citizens who are under attack. Pressure must be brought to bear on Nigeria from the international community."
He continued, "Boko Haram has publicly called for the killing of Christians and stated its aim to Islamise the whole of Nigeria. Fulani militants are now killing more Christians than Boko Haram fighters. In so doing, they appear to be serving the same Islamist agenda.
"This has been going on for far too long. How many more innocent men, women and children need to suffer before something is done? The world must wake up to what is happening in the most populous nation in Africa."