A British optician kidnapped in Nigeria was shot dead after trying to cheer his fellow hostages by playing "Amazing Grace" on his acoustic guitar, two of his fellow missionaries have told The Telegraph.

Ian Squire, 57, was killed instantly after being hit by a salvo of shots fired by one of the gunmen that abducted the four-strong missionary team from their clinic in the southern Delta region on October 13.

Details of how Mr Squire died had previously not been made public, and it had earlier been reported that he had died of an asthma attack after being unable to access medication.

However, an interview with the Telegraph, his fellow hostages David and Shirley Donovan say that he was killed the morning after they were abducted by the gang, who hid them in a bamboo hut in a remote swamp.

The couple said that the gunmen refused to ever explain why they opened fire. One possibility is that they intended it as a warning shot after fearing that Mr Squire's guitar-playing could signal the hostages' presence to other locals.