Freed Nigerian schoolboys walk after they were rescued by security forces in Katsina, Nigeria, December 18, 2020. Dozens of schoolboys who were rescued from kidnappers in northwest Nigeria arrived back home on Friday, many of them barefoot and clutching blankets. REUTERS/Afolabi Sotunde

Freed Nigerian schoolboys walk after they were rescued by security forces in Katsina, Nigeria, December 18, 2020. Television pictures showed the boys dressed in dusty clothes, looking weary but otherwise well, getting off buses in the city of Katsina and walking to a government building. REUTERS/Afolabi Sotunde

Freed Nigerian schoolboys walk after they were rescued by security forces in Katsina, Nigeria, December 18, 2020. A week earlier, gunmen on motorbikes raided the boys' boarding school in the nearby town of Kankara and marched hundreds of them into the vast Rugu forest. REUTERS/Afolabi Sotunde

Rescued Nigerian school boys sit together at the Government house in Katsina, Nigeria, December 18, 2020. REUTERS/Afolabi Sotunde

Rescued Nigerian school boys sit together at the Government house in Katsina, Nigeria, December 18, 2020. REUTERS/Afolabi Sotunde

Rescued Nigerian school boys sit in a bus upon their arrival in Katsina, Nigeria, December 18, 2020. REUTERS/Afolabi Sotunde