Some 80 people have been charged with holding an illegal secessionist rally in south-eastern Nigeria, while pretending to hold a religious march.
Massob revives memories of the horrors of the Biafran civil war
Those charged are members of the Movement for the Actualisation of a Sovereign State of Biafra (Massob).
Biafran secessionist calls led to a three-year war in the 1960s in which more than one million people died.
Earlier this year, some 53 people were charged with treason after taking part in a Massob football tournament.
"They came to the state under the guise of a religious crusade, but through our own intelligence report we discovered that they came to hold a Massob rally," state police commissioner Paul Ifeghohi said.
Massob was banned three years ago. It says it is pursuing its objectives for the Ibo people in eastern Nigeria peacefully.
Several Massob members have died in the past three years in clashes with the police in south-eastern Nigeria, where it draws the bulk of its support.
The BBC's Sola Odunfa in Lagos says the government is intolerant of its existence because it revives memories of the horrors of the civil war against Biafra.