The man, in his mid thirties, is said to have stabbed his friend severally, killing him instantly before he fled after the Sunday night incident that occurred in Mathare slum.
“We are looking for him because he is responsible for the murder,” a senior police officer said, adding “there is overwhelming evidence linking him to this killing.”
The suspect’s wife was detained for questioning, but police said they were likely to release her after the investigation.
“She is only assisting us to see if we can get the suspect,” the officer said, “We are also talking to her to get to know more about their relationship and how the killing occurred.”
He confirmed the woman was unlikely to face any charges, but would appear as a witness in the murder once the prime suspect is arrested and taken to court.
So far, the officer said, the woman has told detectives investigating the incident that the man was stabbed after a confrontation with her husband in their house.
Last month, two cases of women killing their husbands over infidelity claims were reported in the same area.