Lagos: Amnesty International on Friday claimed the Nigerian military shot dead unarmed civilians before a march to mark the anniversary of the 1967 Biafran declaration of independence.
Police have said at least 10 people were killed -- five in the town of Onitsha, Anambra state, and five in Asaba, in neighbouring Delta state -- in violence linked to the commemoration on May 30.
The Indigenous People of Biafra (IPOB) movement, which has revived calls for an independent homeland for the Igbo people in southeast Nigeria, claimed at least 35 were killed.
Amnesty said it was unclear exactly how many people lost their lives, as soldiers -- who the army says acted in self-defence -- took away the dead and injured.
But it stated that based on visits to hospitals and mortuaries at least 17 were killed and nearly 50 injured in Onitsha alone.
"The real number is likely to be higher," it added in a statement, saying some of the dead and injured seen by researchers had been shot in the back, indicating they were fleeing at the time.
"Opening fire on peaceful IPOB supporters and bystanders, who clearly posed no threat to anyone is an outrageous use of unnecessary and excessive force and resulted in multiple deaths and injuries," said Amnesty`s Nigeria director, MK Ibrahim.
One person was shot dead as they slept, he added.IPOB has staged regular demonstrations across the southeast since the arrest in October last year of its leader, Nnamdi Kanu, who has been charged with "treasonable felony" and is awaiting trial.
Kanu, who is also head of the banned Radio Biafra, is accused of calling for a separate republic of Biafra, nearly 50 years after a previous declaration of independence sparked a civil war.
The fighting between 1967 and 1970 left more than one million people dead, most of them from starvation and disease, as the Igbo nation was blockaded into submission.
The May 30 protests were to commemorate the 49th anniversary of the independence declaration.
Amnesty, which said it had spoken to 32 eye-witnesses in Onitsha, said it had seen "no evidence" the killings by the police and military were to protect lives.
The police have said officers opened fire because IPOB members shot at the security forces deployed to monitor the protests and that two police were killed in Asaba.
"Amnesty International cannot confirm this claim. However, such killings would not substantiate the army`s argument they acted in self-defence," it added.
There was also no evidence to support the claim that IPOB opened fire first.
IPOB maintained the protesters were unarmed and one man interviewed said he threw stones but the military and police fired back teargas then used live ammunition.
Another said soldiers stormed a church where protesters were sleeping the night before the march and let off teargas, while another said he saw a young boy shot dead as he had his hands up.The Amnesty report echoes multiple claims about the tactics of armed police and soldiers made by protesters who attended three previous IPOB demonstrations from November to February.
Group members told AFP last month that injured and dead protestors were carted away and dumped in mass graves while others disappeared.
Similar claims have been made against the military in operations against a Shiite Muslim group in December last year, when at least 350 protesters were said to have been shot dead and buried.
The military has also faced repeated charges from human rights groups about abuses against civilians during Boko Haram`s Islamist insurgency in the northeast.
On Biafra, President Muhammadu Buhari has said he "will not tolerate" threats to Nigeria`s unity.
Ibrahim added: "This is not the first time that IPOB supporters have died at the hands of the military.
"It is becoming a worrying pattern and this incident and others must be immediately investigated," he said, calling for an end to "the pattern of increased militarisation of crowd control".