Islamist terrorist groups causing havoc in northern Nigeria are set on "killing Christians" and "destroying Christianity", a bishop has warned. 

Bishop Matthew Kukah, of Sokoto, said that Christians in the north of the country are "marked men and women", according Aid to the Church in Need.

He gave the ominous warning while delivering the homily at the funeral of 18-year-old Catholic seminarian, Michael Nnadi, who was murdered after being abducted from the Good Shepherd Seminary in Kaduna last month. 

"For us Christians, this death is a metaphor for the fate of all Christians in Nigeria, but especially northern Nigeria," he said.

"For us Christians, it would seem safe to say that we are all marked men and women today."

Nnadi was one of four seminarians abducted from Good Shepherd on January 8.  The other three were later released. 

Bishop Kukah went on to say that the north of the country "has become one large graveyard, a valley of dry bones, the nastiest and most brutish part of our dear country". 

The last few months have seen a number of brutal attacks against Christians in Nigeria. 

Last month, 13 Christians were killed by armed Fulani herdsmen in Plateau State on the same day as Nnadi and the other seminarians were abducted. 

On December 26, 11 Christian aid workers were killed in Borno State by the Islamic State in West Africa Province. 

The bishop was critical of suggestions that the attacks do not have a religious element. 

"Are we to believe that simply because Boko Haram kills Muslims too, they wear no religious garb?" he said. 

"Are we to deny the evidence before us, of kidnappers separating Muslims from infidels or compelling Christians to convert or die?"

Bishop Kukah called on Christians to respond to the violence with peace. 

He said: "Are we angry? Yes, we are. Are we sad? Of course, we are. Are we tempted to vengeance? Indeed, we are. Do we feel betrayed? You bet. Do we know what to do? Definitely. Are we in a war? Yes.

"But what would Christ have us do? The only way He has pointed out to us is the non-violent way. It is the road less travelled, but it is the only way."