A number of people taking part in a protest against police brutality have reportedly been shot dead or injured in Nigeria's biggest city, Lagos.
Witnesses said up to 12 people were killed and others wounded when soldiers opened fire. Amnesty International said it had "credible reports" of deaths.
The state governor, however, said there had been no fatalities, although about 25 people had been wounded.
The authorities have promised an investigation into the shooting while an indefinite 24-hour curfew has been imposed on Lagos and other regions.
Amid the rising tensions, President Muhammadu Buhari appealed for "understanding and calm".