Islamic State hostage Peter Kassig was drawn to Islam before his capture, according to a fellow-prisoner who was imprisoned with him for four months.

French journalist Nicolas Henin, who was also imprisoned alongside Alan Henning, David Haines, Steven Sotloff and James Foley, who have all been murdered, gave vivid details of the life the men shared. They were kept in a windowless cell with only a bucket for sanitation, regularly beaten and had barely adequate quantities of food.

Peter Kassig, now known as Abdul-Rahman Kassig, served briefly in the US army in Iraq before leaving and founding a humanitarian charity. He was attracted to Islam while working in Syria.

Henin said of him and of other hostages who converted: "They practised the five daily prayers and would even sometimes perform two extra prayers that are not mandatory at night. Sometimes they would fast on Mondays and Thursdays, which are extra fasts. Just like during [the Muslim celebration of Ramadan] they didn't eat or drink or do anything from sunrise to sunset ... like good Muslim observants, or dedicated Muslims."

He told the BBC's Paul Wood: "Peter told me about how important Islam was to him, how much it helped to overcome his situation in captivity. And he was a very dedicated Muslim. He gave me the impression that he was a bit fragile, but that Islam was strengthening him."