A Christian missionary to Kenya has been sent to prison for 40 years for sexually abusing children at an orphanage in Nairobi, Kenya.

According to the original criminal complaint, Matthew Lane Durham raped more than 10 children, some as young as four years old, including at least one who was HIV positive.

Durham, 21, was guilty of heinous crimes on the most vulnerable victims, said the Oklahoma Federal court.

Durham visited Upendo children's home in Kenya's capital, Nairobi, to work as a volunteer four times between 2012 and 2014, with the latest visit taking place between April and June 2014.

Upendo means "love" in Kiswahili.

During a preliminary hearing, Durham told Upendo staff he must have been possessed by "evil spirits" because he could not rememer the events.

According to the BBC's Abdinoor Aden, the children's home welcomed the sentence. "It is a new beginning for them," said the orphanage founder Eunice Menja.

Earlier she told the court that Durham's abuse was not only "a betrayal of the Upendo mission' but also of the trust Upendo placed in him.

"Matthew Durham defiled the children. Matthew has no remorse," she said. After he was caught, he continued to deny the charges.

Judge David Russell said Durham was the children's "worst nightmare come true".

Durham was also ordered to pay restitution of $15,863.