A teenage Christian girl in Uganda who was locked up by her father for three months after he found out she had converted from Islam, and survived only because her brother was able to secretly give her food and water, is making a miraculous recovery.

Susan Ithungu, now 16, had to hide her faith from her father, a Muslim witchdoctor, Open Doors reports.

But after her mother left the family, he found out and locked her up in a room without food and water. Her younger brother dug a hole in the ground and managed to pass her rations to get by when their father wasn't there.

Earlier reports said Susan was tortured by her father, and sometimes had only muddy water to drink.

In October 2010, three months after she was first imprisoned, Susan was discovered by neighbours, who told the authorities of her plight.

"When they opened the door [of the room], I felt peace and I knew that God had sent me help," she told Open Doors.

However, she was seriously ill and malnourished, and suffered from dental problems, bone fractures, could no longer walk and was emotionally scarred.

Now six years on, Susan has recovered though the help of doctors and emotional and spiritual support from her church, and wants to train as a medic so she can help other people. She still uses crutches to walk and needs further corrective surgery, but it's a far cry from where she once was.

She regularly spends weekends at the house of her pastor, Evangelist Paul, and insists that she has forgiven her father. "I forgive my father because he did not know what he was doing. I have also forgiven my mother for deserting us," she said.

"Please pray for my healing. I want to walk without the crutches. Please pray that the Lord will bless and take care of Evangelist Paul and his family. I am also thankful for the support from Open Doors," she added.

Open Doors has covered the cost of Susan's medical and education expenses.