CHICAGO — Mayor Rahm Emanuel announced on Sunday that the city would soon increase the number of police officers wearing video cameras, an expansion of a pilot program started in January in one police district.

The announcement came five days after Chicago officials released video from a police dashboard camera of a white police officer shooting a black teenager 16 times, even after he had fallen to the ground. Since the video’s release, protesters have held demonstrations almost daily, complaining, in part, that Mr. Emanuel and other city leaders fought for months to keep the graphic video from becoming public, and released it only after a county judge ordered them to do so.

The officer, Jason Van Dyke, was charged with murder in the death of the teenager, Laquan McDonald, but critics have pointedly noted that the charges came more than a year later, and only after it was clear that the videotape would be made public. “Sixteen shots and a cover-up!” marchers chanted on Friday as they blocked store doors along gleaming North Michigan Avenue on one of the busiest shopping days of the year. On Saturday, the protests continued, the Chicago police said, and four people were arrested on misdemeanor charges of obstructing traffic and reckless conduct.

“Improving public safety and making Chicago a safer city has been one of my highest priorities,” Mr. Emanuel said in a statement on Sunday about the police body cameras. “Expanding this successful program into one-third of the city will help enhance transparency and credibility as well as strengthen the fabric of trust that is vital between police and the community.”