Hundreds of people in southern Nigeria have been protesting about the continued detention of Nnamdi Kanu, an activist who supports the creation of a breakaway state of Biafra.
The director of banned Radio Biafra was arrested last month and is still being held despite a court order to free him, his mainly ethnic Igbo supporters say.
There are reports of violence during a protest in Port Harcourt.
Biafran secessionists fought a three-year civil war that ended in 1970.
More than one million people lost their lives before the uprising was eventually quelled by the military.
Secessionist groups have attracted the support of many young people in the south-east in recent years.
The BBC's Abdussalam Ahmed in the south-eastern city of Enugu says in reality they do not want a repeat of the civil war but are keen to draw the attention of the central government to some developmental challenges the region faces.
Activists told the BBC that five people were killed and several others injured after police fired shots and teargas to disperse the protesters in Port Harcourt - the largest city in the region.
But police spokesman Ahmad Muhammad said this was untrue.
"Measures have been put in place to handle the situation in such a way that public peace is not disrupted and to ensure life and property are protected," he told the AFP news agency.
Protests were also held on Tuesday in the city of Owerri in Imo state, a day after the region's biggest market in the city of Aba was reportedly shut down by protesters.
Our correspondent says the protests started peacefully on Friday in the oil-rich Delta state and has since taken place in five other major cities in the region.
The demonstrators are mostly young men holding Biafra flags and banners with pictures of Mr Kanu, who is also a leader in the secessionist Indigenous People of Biafra (IPOB).
"We won't give up until our director Nnamdi Kanu is released," one protester told our reporter during a protest in Enugu.
It is not clear where Radio Biafra is based but it mainly broadcasts to the Igbo-speaking south-east of the country.
The Nigerian government says it has been operating without a licence and began jamming its signals in July, but its broadcasts are still available online and via mobile phones by a dialling a local number.
An IPOB leader, Uchemna Madu, told the BBC that the group was fighting against the "injustice and inequality" ethnic Igbos faced in Nigeria.
"We believe in Nigeria, we have businesses everywhere in the country but we are getting nothing apart from political and social marginalisation," he said.
"Our lives and properties are not secured, we want to live on our own."
The Nigerian authorities have always maintained that most of the issues the Biafra activists are complaining about are not unique to southern part of the country.