A number of people taking part in a protest against police brutality have reportedly been shot dead or wounded 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.
An indefinite 24-hour curfew has been imposed on Lagos and other regions.
On Wednesday, police in different districts of Lagos fired shots in the air to disperse protesters defying the curfew, the BBC's Nduka Orjinmo reports from the capital, Abuja.
Protesters who briefly gathered again at the Lekki toll gate - where Tuesday's shootings took place - were forced out by police, he adds.
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Protests over a now-disbanded police unit, the Special Anti-Robbery Squad (Sars), have been taking place for two weeks. The protesters are using the social media hashtag #endsars to rally crowds.
Reacting to Tuesday's shootings in the wealthy Lekki suburb, former US Secretary of State Hillary Clinton called on Nigerian President Muhammadu Buhari and the army "to stop killing young #endsars protesters".
Former US Vice-President Joe Biden - who is standing against President Donald Trump in next month's election - urged Nigerian authorities to cease the "violent crackdown on protesters".
"The US must stand with Nigerians who are peacefully demonstrating for police reform and seeking an end to corruption in their democracy," he said in a statement.
Nigerian footballer Odion Jude Ighalo, who plays for Manchester United, accused the Nigerian government of killing its own citizens. "I'm ashamed of this government," he said in a video posted on Twitter.
What do we know about the shooting?
Eyewitnesses spoke of uniformed men opening fire at the Lekki toll gate on Tuesday evening.
Armed soldiers were seen barricading the protest site moments before the shooting, BBC Nigeria correspondent Mayeni Jones reports.
Social media footage streamed live from the scene shows protesters tending to the wounded.