The toll was unclear, but witnesses said several people were shot during escalating protests in Lagos. The governor said ‘miscreants’ had hijacked mostly peaceful demonstrations.

LAGOS, Nigeria — Nigerian security forces opened fire Tuesday night at a demonstration in Lagos against police brutality, hitting several people according to witnesses, in a major escalation of the unrest that has gripped the country for two weeks.

The extent of the casualties was unclear, but some witnesses reported seeing people who were killed. Videos posted to social media crackled with apparent gunfire and showed people who were wounded and uniformed forces shooting into the air.

A police officer who witnessed the episode and spoke on condition of anonymity said that 11 people had been killed. But that report that could not be immediately corroborated.

The shooting came toward the end of a day of mounting violence in multiple cities, with the national police deploying riot squads in the capital, Abuja, in Lagos and elsewhere. The unrest spread even after President Muhammadu Buhari attempted to respond to the protesters’ demands by announcing last week that he would disband a special unit of police officers accused of brutalizing people.

Adding to the sense of spiraling chaos, officials said about 2,000 inmates had escaped on Monday in a prison break in Benin City, in southern Edo state.

After news reports early Tuesday that police had killed two or more people in Lagos, the country’s largest city and economic hub, a crowd set a police station there ablaze. Despite the violence and a curfew declared by the governor of Lagos State, protesters refused to disband, blocking roads and demanding that police officers accused of wanton violence be put on trial.

Uniformed forces were deployed to the Lekki Toll Gate area, an upscale suburb of Lagos, where the biggest ongoing protests have been held, largely peacefully, since October 7. Beginning at around 7 p.m. on Tuesday, some of them began firing — shortly after the streetlights unexpectedly went out and security cameras were removed from the scene, witnesses said.

A protester streaming the scene live on Instagram, Obianuju Catherine Udeh, a disc jockey who goes by DJ Switch, said she counted seven casualties around her. Sporadic gunfire went on for about an hour.

On Monday, Lagos inaugurated a panel of inquiry to investigate allegations of abuse, but proceedings have not begun. Three other states have also made the same move.

In the massive prison break, a spokesman for the interior ministry in charge of correctional facilities, Mohammed Manga, said armed crowds had attacked two correctional facilities in Benin City and overpowered guards on duty. He said 1,993 inmates were missing; it was not clear how many inmates were held before the attack.

“Most of the inmates held at the centers are convicted criminals serving terms for various criminal offenses, awaiting execution or standing trial for violent crimes,” Mr. Manga said.