Protesters have come under gunfire in Nigeria’s biggest city, Lagos, eyewitnesses and local media say, amid continuing anger over police brutality.
Who opened fire and the number of casualties is unclear, but Amnesty International said it had credible reports of deaths.
An indefinite 24-hour curfew has been imposed on Lagos, the commercial hub.
Other regions are also imposing curfews after two weeks of protests that began over a now-disbanded police unit.
Eyewitnesses spoke of uniformed men opening fire in the wealthy Lekki suburb of Lagos on Tuesday evening.
Armed soldiers were seen barricading the protest site moments before the shooting, BBC Nigeria correspondent Nayeni Jones reports.
It is not yet clear how many people were injured or killed, but social media footage streamed live from the scene shows protesters attending to the wounded.
In a tweet, Amnesty International Nigeria said it had “received credible but disturbing evidence of excessive use of force occasioning deaths of protesters at Lekki toll gate in Lagos”.
Amnesty International spokesman Isa Sanusi later said: “People were killed at the tollgate by security forces… we are working on verifying how many.”
The Nigerian authorities have not yet commented.
How did the unrest begin?
Protests began nearly two weeks ago with calls for a much-hated police unit, the Special Anti-Robbery Squad (Sars), to be disbanded.
President Muhammadu Buhari did then dissolve the unit, which had been accused of illegal detentions, assaults and shootings, on 11 October.
But the demonstrators called for more changes in the security forces as well as reforms to the way the country is run.
Lagos state Governor Babajide Sanwo-Olu has said that criminals have hijacked the protests “to unleash mayhem”.