A court in Nigeria on Thursday sentenced Nnamdi Kanu to life in prison after convicting him on all seven terrorism-related charges at the end of a decade-long trial that has inflamed tensions in the country's southeast.

Judge James Omotosho said prosecutors proved that his broadcasts and orders to his now banned Indigenous People of Biafra (IPOB) group incited deadly attacks on security forces and citizens.

Security was tight around the Abuja court amid fears of protests and violence. Analysts warn that the conviction could stoke separatist sentiment and complicate efforts to restore calm in the region, where authorities blame IPOB for a wave of deadly attacks.

Omotosho declined the prosecutors' request for a death penalty, saying he must "temper justice with mercy" despite Kanu's arrogance and lack of remorse.

"The death sentence globally is being frowned upon by the international community so consequently and in the interest of justice, I hereby sentence the convict to life imprisonment," he said.

"His intention was quite clear as he believed in violence. These threats of violence were nothing but terrorist acts, which were duly carried out by his followers," Omotosho said.