The charges against Mr Kanu, who leads a banned group called the Indigenous People of Biafra (Ipob), are linked to broadcasts he made in support of the secession of the mainly Igbo-speaking region of south-east Nigeria.
Five years ago while Mr Kanu was on bail, he fled the country.
But he was controversially captured last year – reportedly in Kenya – and taken back to Nigeria.
Despite low level clashes in the south-east, the pro-Biafra movement says it wants to achieve independence without violence, and has mounted a civil disobedience campaign, crippling local economic activity.
