A pastor has claimed ISIS are boosting their funds by selling shrunken heads from their decapitated victims on auction websites. The religious preacher claims that the terrorist group are peddling sick mementos of their murderous crimes to collectors. American pastor Harry Walther, from Montana, USA, says ISIS has cottoned on that collectors of grisly curios are willing to pay more than 500 US dollars (about £346) for a shrunken head. And with the terrorists staging public executions, decapitating thousands of prisoners and 'non-believers', the extremist cell has a huge number of heads to sell. Walther claims terrorists can read up on online instructions telling them how to 'shrink' a human head and passing it off as an ancient tribal curio. The preacher, in his early fifties, says the Bible's Book of Revelations predicted that hundreds of millions of Christian men, women and children will be beheaded for their faith in Jesus. He said: "In Revelation 9, John sees an army of 200,000,000 soldiers wage war against the west. "So as we are told The 'Tribulation Martyrs are greater than any, many could number' - this means there will be more than 200 million beheaded Christians and possibly over 300 million. "What to do with 350 million decapitated heads? "Make shrunken heads and sell them for a king's ransom! "I believe the ancient, Amazonian practice of shrunken heads will be revived and practised on a global scale. "The shrunken heads of the Christian martyrs could be shrunken to baseball size and sold as New Age 'souvenirs'. "According to satanic belief, these heads will be more prized than silver and gold. "During The Holocaust, the Nazis made shrunken heads from decapitated Jewish prisoners and hung them in the jail cells to terrify Jews into following orders and taking their 'showers' (poison gas chambers). "So 350 million decapitated heads sold at $1000 (£690) a head comes to $350 billion (£241 billion) dollars! "Even if the shrunken heads of Christians start at $100 (£69) and range up in price from $500 (£345) or more, we are still talking about hundreds of billions of dollars made as the love of money drives mankind to commit the ultimate acts of human atrocities. "If you think this is sick, I will tell you what is really sick. "You can purchase REAL shrunken heads. You can purchase kits to make shrunken heads from goat skins. Children can buy 'kits' to make imitation shrunken heads for Halloween." The claims come after ISIS released a video of a British-speaking teenager beheading a hostage in a sick propaganda film.