BRUSSELS (AP) — Belgian prosecutors have requested the appointment of an investigative judge following the death of a 23-year-old Black man who was detained by police last week in Brussels.

The Brussels prosecutor's office announced the request Wednesday as around 300 protesters, some of them holding Black Lives Matter signs, gathered in Belgium's capital Wednesday asking for authorities to shed light on the circumstances surrounding the man's death on Saturday night. He was publicly identified only with the initials I.B.

The prosecutor's office said I.B. was arrested after he allegedly tried to run away from police officers checking a group of people gathered in downtown Brussels despite COVID-19 measures restricting social gatherings. He was taken to a police station where he fainted and then transferred to a hospital, where he was pronounced dead, the office said.

The prosecutor's office said Belgium's Comité P, an independent body overseeing police services, is investigating and a coroner has been appointed to perform an autopsy as well as toxicology tests.

Belgian media reported that I.B. had started to record the police with his smartphone on Saturday when officers decided to carry out an ID check on him. The prosecutor's office said it has seized video surveillance images, both from the police station and at the scene of the man's arrest.

His family and lawyer met with the chief prosecutor on Wednesday morning. The prosecutor's office said they were given guarantees that “all means are and will be implemented to shed light on what happened."

The demonstration in downtown Brussels was largely peaceful, although some participants later threw objects at police officers and set fires in the street. At one the car of Belgium's King Philippe passed close to protesters, and the driver changed routes under police protection.

The Royal Palace told The Associated Press the king was inside the car but never in a dangerous situation.

___

Sylvain Plazy, Mark Carlson and Francisco Seco in Brussels contributed to this story.