The US city of Baltimore has declared a state of emergency amid violent protests over the death of a black man fatally injured in police custody.

A week-long curfew has been announced and as many as 5,000 National Guard troops could be deployed.

After dark, a community building that was under construction was engulfed in flames.

Earlier, dozens of people were seen confronting police, and 15 officers were injured.

African American Freddie Gray, 25, died on 19 April after a week in a coma. The justice department is investigating exactly where and when his spinal injuries were sustained.

Officials have suspended six police officers who were involved in the case.