Nigerian police have clashed with pro-independence ethnic Igbo activists ahead of their leader's treason trial.
Massob's leader goes on trial on Tuesday
Riot police fired tear gas as they battled to clear burning barricades in the south-eastern city of Onitsha.
Police spokesman Haz Iwendi told the BBC there had been some arrests and said reinforcements were being sent to the city from neighbouring states.
The Igbos fought to break away from the rest of Nigeria during a three-year civil war that ended in 1970.
Mr Iwendi said police had used tear gas and rubber bullets to disperse protesters but denied live bullets had been fired.
The protest was called by the banned Movement for the Actualisation of the Sovereign State of Biafra (Massob).
Spokesman Uchenna Madu told the BBC that police had been raiding the homes of activists and chasing them out.
Some 1m died during the Biafran civil war
He also alleged that they had fired live bullets.
"What we are doing is civil disobedience against the oppression and marginalisation of Biafrans. We have told them time without number that we are no longer part of Nigeria. We are Biafrans in soul and body," Mr Madu told AFP news agency.
"This is a peaceful protest. We are not causing trouble or violence. They should allow us to go because every people has the right to self-determination," he said.
Massob leader Ralph Uwazurike and six others are due to appear in court on Tuesday.
Charges against the men include training a Massob army and unlawfully running a society with the aim of waging war with the federal state.
If found guilty they could face the death penalty, though life imprisonment is more likely.
Several Massob members have died in the last three years in clashes with the police in south-eastern Nigeria, where it draws the bulk of its support.
In 1967, General Emeka Ojukwu led the region in a revolt against federal rule. It was put down after a bloody civil war in which about a million people died.