Youth-led demonstrations in Nigeria began against police abuse, quickly spiralling in broader calls for reform.

But they ended weeks later when security forces shot at demonstrators in Lagos -- killing at least 12 people, according to Amnesty International.

At a judicial panel the army denied using live rounds but the government vowed to disband the much-hated police unit, the Special Anti-Robbery Squad (SARS), which had been the main target of protests over brutality.

"Nigerian authorities have failed to bring to justice those suspected to be responsible for the brutal crackdown by security forces on peaceful #EndSARS protesters at Lekki toll gate and Alausa in Lagos in October 2020 and have brazenly attempted to cover up the violence," Amnesty said.

"Since the assault by security forces, which killed at least 12 people, Nigerian authorities have targeted supporters of the protests against police brutality by the disbanded SARS," Amnesty's country director Osai Ojigho said in the statement, released to mark 100 days since the shootings.

She said some of the movement's supporters have had their bank accounts frozen.

Amnesty challenged the Nigerian government to suspend accused officials, pending investigations, and to ensure victims access to justice.

In November, the Lagos State government set up a panel of inquiry to investigate the bloodshed and wider allegations of abuses by SARS featuring testimony by the army that presented videos to back its claims.

The government has promised a string of reforms in response to the protests, and disbanded SARS, replacing it with another security forces called SWAT.

Nigeria, where the median age is 18, is a tinderbox of deep economic and social grievances, and the demonstrations snowballed from anger over police violence to broader demands.