Death-row inmate Celestine Egbunuche has been dubbed Nigeria's "oldest prisoner" amid a campaign calling for his release.

He is 100 years old and has spent 18 years in jail after being found guilty of organising a murder.

Small and slightly hunched over, he looks wistfully into space as he sits on a tightly packed bench inside a stuffy prison visitor's room.

Dressed in a white T-shirt, shorts and flip-flops, he lifts his head slowly - his way of acknowledging our presence.

But otherwise he remains quiet during our visit - in stark contrast to the rest of the room that is filled with loud chatter at Enugu Maximum Security Prison in south-east Nigeria.

His son Paul Egbunuche, 41, sits protectively close to him - and does the talking. He is in jail on the same murder charge.

They were both accused of hiring people to kidnap and kill a man over an alleged land dispute in Imo state.

Paul maintains their innocence. They were detained in June 2000 and eventually convicted and sentenced to death in 2014.

It has not been possible to contact the family of the man who was killed - even the Nigeria prison service has been unable to find them.

'Confused and childlike'

As prison officials look on, he tells me that his father isn't really able to talk much any more and is no longer aware of his surroundings.

"When you ask him something, he says something else. The doctor told me that it is his age, he has become like a little pikin [child].

"There are some times when he will ask me: 'These people here [inmates], what are they doing here?'"

Paul says he rarely leaves his father's side now; he has been his primary carer since his health began to deteriorate in prison.

These health problems include diabetes and failing eyesight - and Paul uses what he can to manage them.

"The only thing I'm using to manage him is food, unripe plantain, and they [officials] give him some drugs."

Father and son share a cell with other death-row prisoners, who are separated from the general population.

"When I wake up in the morning, I will boil water and bath him," Paul says. "I'll change his clothes then prepare food for him. If they open up [the cell] I'll take him out so the sun will touch him.

"I'm always close to him, discussing with him and playing with him."

Paul says the other inmates sometimes help him care for his father and that many of them want his father to be released.

It was after his father's 100th birthday on 4 August that events were set in motion that may lead to his release.

A photo of Paul and a frail looking Egbunuche went viral in August after a local paper did a story about him turning 100 in jail. It sparked a debate about the length of time Nigerians spend on death row and the place of capital punishment altogether.

The latest figures from the Nigerian Prisons Service show that more than 2,000 people are on death row in Nigeria, many of whom spend years waiting to be executed.

The death sentence is not commonly carried out in Nigeria. Between 2007 and 2017, there were seven executions - the last one taking place in 2016, Amnesty International reports. (BBC)