Aid agency Save the Children says Islamist militants are beheading children as young as 11 in Mozambique's northern province of Cabo Delgado.
One mother told the agency she had had to watch as her 12-year-old son was killed in this way close to where she was hiding with her other children, reporst the BBC.
More than 2,500 people have been killed and 700,000 have fled their homes since an Islamist insurgency began in 2017.
The militants have pledged allegiance to the Islamic State (IS) group.
In its report, Save the Children said it had spoken to displaced families who reported gruesome scenes in the gas-rich province.