Sierra Leone UN-backed tribunal said on Wednesday it will grant conditional early release to a former rebel leader, Augustine Gbao, who is in prison for crimes against humanity during the country's brutal civil war.

Gbao, 72, a former leader of the Revolutionary United Front (RUF), had served 17 years of a 25-year sentence for acts including terrorism, extermination, murder, rape and sexual slavery.

"Former RUF commander Augustine Gbao has been granted conditional early release, with a three-month delay, during which time he must undergo specific training geared to his understanding of and acceptance of responsibility for the harm he inflicted by his crimes," the court said in a statement released Wednesday.

The court found that Gbao, who was detained in 2003 and is serving his sentence in Rwanda, had "largely behaved properly in prison" and showed remorse, it said.

Gbao will be able to serve the remainder of his sentence in his community of Blama, a town in Sierra Leone's Eastern Province, subject to close supervision and strict conditions.

The conditions include a radio and television apology to the victims of his crimes and to the people of Sierra Leone.

Between 1991 and 2001, the RUF carried out a series of atrocities in order to try to gain control over Sierra Leone's lucrative mining districts.

During the 2009 sentencing for Gbao and two other RUF leaders, the court said the rebels terrorized the civilian population with mass killings, rape and amputations.