Chad's armed forces and Chadian and Sudanese rebel groups are recruiting children as young as 13 to become soldiers, Amnesty International said in a report released Thursday.

Sudanese President Omar al-Bashir is in Chad for a regional summit, and human rights groups are pleading for his arrest. Bashir presided over the conflict in Darfur, where an estimated 300,000 people were killed and over 2.5 million displaced.

"Women who fled violence in Sudan's Darfur region are being regularly raped in refugee camps in neighbouring Chad, despite the presence of U.N.-trained forces, Amnesty International said on Wednesday.

"This week the African Centre for Justice and Peace Studies (ACJPS) reported on a series of attacks on the civilian population in North Darfur by Chadian rebel groups.