An elderly Christian widow who was forced by ISIS militants to convert to Islam, spit on a crucifix and hand over all her belongings under threat of execution has told her story for the first time after her town was liberated.

Speaking to Reuters on Sunday, 77-year-old Zarifa Badoos Daddo recalled being left behind in Qaraqosh – a major Christian town near Mosul in Iraq – when militants overran the region in August 2014.

While tens of thousands of people fled, Daddo and another elderly woman stayed.

ISIS militants knew they were there and allowed them enough food to survive. The jihadists did, however, intimidate the women and try to convince them to follow Islam.

"They told me to spit on the crucifix. I was crying inside but I couldn't show it," Daddo told Reuters, adding that ISIS members also made her stamp on a picture of the Virgin Mary.

"We were two women living by ourselves. They would come at night, sometimes they would come at four in the morning, so we were scared," she recalled.

"They would say, 'Sister don't be scared, we are your brothers. You are one of us now.'"

Jihadists stole all her belongings of any worth, and then threatened to shoot her if she didn't hand over all her money, telling Daddo: "If you don't give us your money, we will empty this machine gun in your chest."

When they tried to force her to convert to Islam, the widow said: "What is the difference between a Muslim and a Christian? We all worship God", but eventually she bowed to their demands. "My life is dear to me so I said what I had to," she said.

Qaraqosh was liberated just over a week ago as part of a major offensive to retake Mosul – ISIS' last stronghold in Iraq – led by Iraqi troops and coalition air forces. Daddo was on Sunday reunited with her family after being found sheltering in a house.

Qaraqosh was once home to the largest Christian community in Iraq, but thousands fled after ISIS occupied the town and issued an ultimatum: leave, convert to Islam, pay a heavy tax or be killed.

Before the Iraq invasion of 2003 there were more than 1.5 million Christians living in Iraq. There are now believed to be only around 200,000.