Roughly 115 million boys around the world were married off as children, the United Nations said in a new study on Friday.

It said one in five of them, or 23 million, were married before the age of 15, Anadolu Agency reported.

The United Nations Children's Fund (Unicef) released its first-ever in-depth study of child grooms using data from 82 countries spanning sub-Saharan Africa, the Caribbean, South Asia and East Asia.

"Early marriage brings early fatherhood, and with it added pressure to provide for a family, cutting short education and job opportunities," said Unicef executive director Henrietta Fore in a press release.

The study found that the Central African Republic has the highest rate of child marriage among boys followed by Nicaragua and Madagascar.

The latest figures from the study bring the total number of people, both male and female, that married as children to 765 million. Girls are disproportionately affected by child marriage: one in five women, aged 20 to 24, were married before the age of 18 compared with one in 30 boys or young men that were married as children.

"Children most at risk of child marriage come from the poorest households, live in rural areas, and have little to no education," the study found.

The UN considers marriage before the age of 18 a fundamental violation of human rights.

- Bernama