LAGOS, Nigeria (AP) — Plumes of smoke rose from a prison in Nigeria's largest city and gunfire could be heard as people ran through streets in the area on Thursday, signs of continued unrest in the West African nation that has been gripped by protests against police brutality.

It was not clear what was happening at Lagos' Ikoyi Correctional Center, known for its overcrowded cells holding people awaiting trial. But prisons and police stations have been broken into over the past two weeks as anger at authorities boiled over and some sought to take advantage of the protests to create mayhem. Officials did not immediately comment on the situation at the prison.

Elsewhere in the sprawling city of 14 million, the streets were empty and shops were shuttered, as residents largely obeyed a government curfew meant to curb the chaos. For two weeks, protesters have taken to the streets peacefully. But on Wednesday, mobs vandalized and burned police stations, courthouses, TV stations and a hotel. Smoke billowed from several locations in the city as police battled angry crowds with tear gas and gunfire.

Some protesters active on social media disavowed the violence, saying their demonstrations had been hijacked by criminals.

Wednesday's violence came a day after security forces fired into a crowd of thousands of protesters, according to Amnesty International, killing 12. At least 56 people have been killed during the protests, Amnesty said. That shooting drew outrage and brought new attention from around the globe to the protests.

The #EndSARS demonstrations began in early October with calls for Nigeria’s government to shut down the police Special Anti-Robbery Squad, known as SARS. The government has agreed to disband the unit, but the protesters have now broadened their demands to include more widespread reforms to end human rights abuses and pervasive government corruption.

Nigeria has massive oil wealth and is one of Africa’s largest economies, but many of its more than 200 million people face high poverty levels and lack basic services — because of rampant graft, according to rights groups.

President Muhammadu Buhari — who has said little about the protests engulfing his country — did not mention the Lekki shootings in a statement Wednesday but issued a call for calm and vowed police reforms.

U.N. Secretary-General Antonio Guterres told The Associated Press in an interview Wednesday that the right of Nigerians “to protest peacefully needs to be guaranteed.”

He said “police brutality needs to stop, and those responsible for acts of such dramatic violence are made accountable.”

Guterres said he spoke with Buhari several days ago and believes he “will be able to bring things into a normal way to respect the rights of assembly of people, and to make sure that those that misbehaved are held accountable.”