The UN children’s agency Unicef has called on the Nigerian authorities to urgently review an Islamic court’s decision to sentence a 13-year-old boy “Umar Farouq” to 10 years in prison for blasphemy.

The boy was convicted in August of making uncomplimentary remarks about God during an argument with a friend in northern Kano state.

Kano is one of 12 Nigerian states practising the Sharia legal system alongside the country’s secular laws.

Muslims form the majority in the north.

Umar was handed the jail sentence by Aliyu Kanu, the same judge who passed a death sentence on Kano musician Yahaya Sharif-Aminu for blasphemy, after being found guilty of using “disparaging language on Allah” during a disagreement with his friend.

The 13-year-old’s sentencing “negates all core underlying principles of child rights and child justice that Nigeria – and by implication, Kano state – has signed on to”, said Peter Hawkins, Unicef’s representative in the West African state.

On 9 September, the boy’s lawyer, Kola Alapinni, said he had filed an appeal against the judgement.

“This is a violation of the African Charter of the Rights And Welfare of a Child. A violation of the Constitution of the Federal Republic of Nigeria,” he added.

He told the BBC that no date had been set for the appeal to be heard in court.