Protests in Nigeria over police brutality
Anger has been brewing on social media after the video of the alleged killing in the southern Delta state, which authorities denied was real.
The man who filmed the video was arrested, provoking even more anger.
Hundreds of youths gathered in Ikeja in central Lagos holding banners reading "Respect for human rights" and "A more equal society."
Several other demonstrations have taken place in recent days across the country, including in the capital Abuja.
The movement initially targeted the federal Special Anti-Robbery Squad (SARS), widely accused of unlawful arrests, torture and even murder, but has since broadened to include all police forces.
While the SARS unit was suspended on Sunday, groups such as Amnesty International said the government had not gone far enough, pointing to previous unsuccesful attempts to ban the force.
There were more than 2.4 million tweets with the hashtag #EndSARS on Friday.
"There's a lot more people than yesterday. The movement is growing," 29-year-old Chinoso Esengba, a doctor participating in Friday's protest, said.
"This problem affects us all; we all risk being tortured, arrested, extorted for no good reason," he added.