U.K.-based charity Save the Children said Thursday that more than three-quarters of school-age children in war-torn Sudan are out of school, creating one of the world’s worst education crises.

A new study by the charity revealed that 13 million out of 17 million school-age children in Sudan are not attending classes.

All 13 million children have been out of school since at least April 2023, meaning they have now lost more than two academic years to violence, the study said.

This figure includes around 7 million children who are enrolled but unable to access education due to ongoing conflict or displacement and another 6 million who are not enrolled at all and risk losing their right to an education entirely, the study showed.

Since April 2023, Sudan has been torn apart by a brutal war between the army and the paramilitary Rapid Support Forces (RSF).

The war has killed tens of thousands, displaced millions and decimated the country's infrastructure, including schools and hospitals.

"If the conflict continues, millions of these children will not be able to go back to school, leaving them exposed to immediate and long-term dangers, including displacement, recruitment into armed groups and sexual violence," said Mohamed Abdiladif, Save the Children's country director in Sudan.

The study comes after the United Nations' fact-finding mission on Sudan said this week that girls as young as 12 were being forced into marriage, sometimes under the threat of death to their families.

Even before the current conflict began, nearly 7 million Sudanese children were already out of school due to poverty and instability, Save the Children said.

It added that just under half of schools in the country have reopened in recent months, allowing approximately four million children to resume their education.

This comes as relative calm has returned to parts of central Sudan, including the capital Khartoum, after the army regained control of the area earlier this year.

Across Sudan, around two million people have made their way back home since November last year, according to the U.N.'s migration agency.

Nearly half of those have resettled in the central Al-Jazira state, followed by Khartoum with over 600,000 returnees.

Sudan is facing one of the world's worst humanitarian crises, according to the United Nations, with famine declared in a number of refugee camps in Darfur.

As of July, nearly 10 million people were forcibly displaced inside the country, while an additional four million had fled across the borders.