Ian Squire, a British national kidnapped in Nigeria’s southern Delta state was killed and three others released, the BBC reported, citing the U.K.’s Foreign Office.
Details surrounding the death of missionary Ian Squire, who was abducted on 13 October, were not immediately clear.
Fellow Christian charity workers Alanna Carson, David Donovan and Shirley Donovan have been released following negotiations.
The Nigerian authorities are now conducting an investigation into Mr Squire’s death, and believe militants operating in the area are behind the abduction.
They say four people have been arrested in connection with the case.
The Foreign Office (FCO) said they were supporting the families of the three released Britons, who have now returned home.
The group, who had been providing “free medical care and religious activities” to the local Enukorowa community, are understood to have been held at militant camps in the creeks and swamps of the delta.
The community were said to be “saddened” by their kidnapping.
The state police said it was “unfortunate” the group had not informed them of their presence, despite living in the area for the past three years.
The families of Mr Squires and the other hostages said the kidnap had been “traumatic for all concerned”.
While their statement said they were “delighted and relieved” for the three freed hostage, they said “our thoughts are now with the family and friends of Ian as we come to terms with his sad death”.
Kidnapping for ransom and armed robbery is common in the west African country, with the FCO advising against “all but essential travel” due to the “high threat of criminal kidnap”.
Oil workers and Westerners are often the target of attacks in the oil-rich Delta Niger region.
Italian priest Maurizio Pallu was kidnapped by armed gunmen near Benin City in southern Nigeria last month, but released after spending three days held in a forest.
High-profile abductions have also bee carried out by Islamist group Boko Haramin northeastern Nigeria.