Islamic State (IS) militants have beheaded four Christian children in Iraq for not converting to Islam, according to one of the only Christian leaders in the country.

British vicar Canon Andrew White, based in Baghdad, claimed the beheadings occurred in a Christian enclave near Baghdad after IS took control.

"Things were bad in Baghdad, there were bombs and shootings and our people were being killed, so many of our people fled back to Nineveh, their traditional home," he told the Orthodox Christian Network.

"It was safer, but then one day, Isis – Islamic State. They came in and they hounded all of them out. They killed huge numbers, they chopped their children in half, they chopped their heads off, and they moved north and it was so terrible what happened."

White revealed the threats made by IS to the Christians, giving the ultimatum that they convert to Islam or face death.

He said: "They said to one man, an adult: 'Either you say the words of conversion to Islam or we kill all your children.'

"He was desperate, he said the words. And then he phoned, me and said: 'Abouna [Father], I said the words, does that mean that Yesua [Jesus] doesn't love me any more?' I said, "Yesua still loves you, he will always loves you.""

He then detailed how the four young Christians boys were killed by the terror group.

"Islamic State turned up and said to the children, you say the words that you will follow Mohammed," White said.

"The children, all under 15, four of them, said no, we love Yesua, we have always loved Yesua, we have always followed Yesua, Yesua has always been with us.

"They said: 'Say the words.' They said: 'No, we can't.' They chopped all their heads off. How do you respond to that? You just cry."