Three people are said to have been killed in a second day of clashes between riot police and stone-throwing youths in a south-east Nigerian city.
Businesses were shut for the day
Igbo activists in Onitsha are angry at the arrest of their leader, who faces trial next month on treason charges.
The protest was called by the banned Movement for the Actualisation of the Sovereign State of Biafra (Massob).
The Igbos fought to break away from the rest of Nigeria during a three-year civil war that ended in 1970.
Massob supporters erected barricades of burning tyres to block roads and police shot in the air to disperse them.
Residents said that at least three people were killed as a direct result of the disturbances.
Most shops and market stalls were closed.
On Monday, police spokesman Haz Iwendi told the BBC that reinforcements were being sent to the city from neighbouring states.
The charges against Massob leader Ralph Uwazurike and six others include training a Massob army and unlawfully running a society with the aim of waging war with the federal state.
Some 1m died during the Biafran civil war
If found guilty they could face the death penalty, though correspondents say 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.
The Igbo are Nigeria's third biggest ethnic group but calls for Igbos across the country to go on strike were ignored outside the south-east.