Washington: Security was beefed up in Baltimore City, just 64 km northeast of the American capital, after it erupted into chaos and violence as protestors, mourning the death of yet another black man in police custody nine days ago, clashed with law enforcement officers.
Maryland Governor Larry Hogan declared a state of emergency Monday and activated the National Guard. The mayor of Baltimore said every possible resource was being deployed to "gain control of this situation".
Clashes left at least 15 police officers injured, according to media reports. With the city imposing a mandatory curfew from 10 p.m. to 5 a.m. daily for a week starting Tuesday, Baltimore City Public Schools were ordered closed on Tuesday.
Monday's violence came the same day as the funeral of Freddie Gray, 25, who was arrested on April 12 and died one week later from a fatal spinal cord injury.
Six officers have been suspended, but investigators say they still don't know how it happened, according to CBS News.
Time magazine recently listed 14 major instances of a white cop shooting dead a black person from 17-year-old Trayvon Martin being fatally shot on Feb 26, 2012 in Sanford, Florida to the April 4 shooting of Walter Scott in North Charleston, South Carolina.
According to a report, 154 persons have died at the hands of law enforcement officers since January with 37 killed in April alone.
"What we see tonight that is going on in our city is very disturbing," Baltimore Mayor Stephanie Rawlings-Blake told reporters on Monday.
Rawlings-Blake also promised to hold those responsible for the violence accountable.
More than two dozen people have already been arrested, CNN reported citing Col. Darryl D. DeSousa with the Baltimore Police Department.
DeSousa described the violence as "unprecedented". A video showed police in riot gear taking cover behind an armoured vehicle, as protestors pelted them with rocks.
The Baltimore Police Department said it had heard reports of protestors setting small items on fire, and footage showed a cruiser in flames.
Video also showed people looting local stores, and an area pharmacy was set on fire after it was ransacked. Thick dark smoke filled the streets, CNN said.
Earlier in the day, the Baltimore Police Department said it had received a "credible threat" that gangs were teaming up to "take out" officers.
Up to 5,000 law enforcement officials will be requested from the mid-Atlantic region to help quell the violence in Baltimore, Col. William Pallozzi of the Maryland State Police said at a press conference late Monday.
Over the weekend, a few protestors vandalised police cars, threw objects at officers, cursed at them and scuffled with them.
Some others smashed squad cars with garbage cans, climbed on top of them and stomped on them, CNN video showed.
Meanwhile, investigators from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives have joined local authorities to investigate the fires around Baltimore, according to a federal law enforcement source.
Police in riot gear, holding large see-through shields, took up positions around Baltimore on Tuesday morning. National Guard members stood outside City Hall.