The full damage wreaked by Boko Haram in Nigeria is yet to be known.

This is according to a report which explores the "devastating impact" the terrorist group has had on education in northeast Nigeria.

The 86-page report from Human Rights Watch (HRW) claims one million children have little or no access to schools as a result of Boko Haram's attacks. This situation is made worse by the Nigerian army's policy of using schools as military bases and therefore increasing the risk of attack.

More than 910 schools have been targeted by the Islamist group, whose name means "Western (or non-Islamic) education is a sin". At least 611 teachers have been deliberately killed and another 19,000 forced to flee. At least 1,500 schools have closed as a result of Boko Haram's attacks.

"In its brutal crusade against western-style education, Boko Haram is robbing an entire generation of children in northeast Nigeria of their education," said Mausi Segun, Nigeria researcher at HRW. "The government should urgently provide appropriate schooling for all children affected by the conflict."

This week marks the two year anniversary of the Chibok school kidnapping which sparked an international campaign to bring back the girls. Of the 276 originally kidnapped, 219 remain in captivity.

In a video released in May 2014 the Boko Haram leader, Abubakar Shekau, said women and girls would continue to be abducted to "turn them to the path of true Islam" and ensure they did not attend school.

The fighting has sparked a largely unreported refugee crisis with an estimated 2.2 million people, including 1.4 million children, displaced. Only around 10 per cent are in government-recognised refugee camps where there is some schooling. The other 90 per cent are with friends and family members with little or no access to education.

Although the Nigerian government declared Boko Haram had been "technically defeated" in December 2015, attacks continue and there is little prospect of refugees returning.

HRW used the report to urge the government to improve education in the northeast and ban the use of schools for military purposes.

Segun said: "Boko Haram's attacks and the government's neglect and misuse of schools have contributed to the dismal state of education in the northeast.

"It is up to both sides to immediately stop the attacks on education and end the cycle of poverty and underachievement to which far too many children in the region are being sentenced."

HRW's report came as a seperate report by Unicef said Boko haram's use of child suicide bombers over the last year had increased. One in five of the group's suicide attacks were now done by children, said the UN's child agency – an 11-fold increase compared to 2014.