A leading academic has claimed that Christians who are recruited and converted by ISIS become the "fiercest"fighters for the regime.

Scott Atran, an anthropologist at Oxford University, was giving evidence to the UN Security Council's counter-terrorism committee about the causes of radicalisation, the Associated Press reports.

He said that "some" Islamic State recruits come from Christian families "and they happen to be the fiercest of all the fighters we find."

Atran also said that most ISIS fighters are not recruited through mosques, but instead by their family and friends.

He told the UN: "It is the call to glory and adventure that moves these young people to join the Islamic State" and that "jihad offers them a way to become heroes."

He argued that young people are attracted to the militant group because of its revolutionary and idealistic ideas. "The Islamic State represents the spearhead of the most dynamic counter-culture revolutionary movement since World War II with the largest volunteer fighting force since World War II," he said, according to the Daily Mail.

He said that the West's counter message about Islamic State's brutality is not working. Atran said he obtained his information through interviews with captured ISIS soldiers.