Amnesty International said there was “credible but disturbing evidence” in the Nigerian city of Lagos that security forces had shot dead over a dozen protesters demonstrating against police brutality.
Many of the shootings occurred in the city”s wealthy Lekki neighbourhood, witnesses and local media reported.
There have been nearly two weeks of protests across many cities against the Special Anti-Robbery Squad (SARS), a police unit that human rights groups have blamed for abuses including violence and torture against civilians.
The Nigerian government has since disbanded the unit, but the protests have continued.
The protest movement, known as #endSARS, has attracted international attention, with Nigerian football stars based abroad and former US Secretary of State Hillary Clinton among those calling on the authorities to end their crackdown.
There have also been cases of looting and arson across the country in recent days.
A 24-hour indefinite curfew has been declared in cities including Lagos, but there was no immediate official confirmation of a fatal shooting in Lekki.
A short statement on Tuesday night from Gbenga Omotoso, the Lagos state commissioner for information, said only that “there have been reports of shooting at the Lekki Toll Plaza following the 24-hour curfew imposed on Lagos.”
“The state government has ordered an investigation into the incident,” it added.
But the daily newspaper Punch called it “Black Tuesday” and said as many as 49 people had been killed across Nigeria.