Enraged protesters have set fire to buildings and cars and looted businesses in Ferguson after a grand jury decided not to indict a white police officer in the death an unarmed black 18-year-old.
Ferguson burned through the night despite pleas for calm from US President Barack Obama and the family of Michael Brown after St Louis County's top prosecutor announced the officer faces no state criminal charges.
Monday night's destruction appeared to be much worse than protests after Brown's August death.
Authorities used tear gas to try to disperse protesters and reported hearing hundreds of gunshots, which for a time prevented fire crews from fighting the flames.
Officer Darren Wilson's fatal shooting of Brown during a confrontation in August ignited a fierce debate over how police treat young African-American men and focused attention on long-simmering racial tensions in Ferguson and around the US.
Monday night's protests were "probably much worse than the worst night we ever had in August" after Brown was killed, said St Louis County Police Chief Jon Belmar, who added police had not yet fired a shot.
He said the fabric of the community has been torn apart in Ferguson, a predominantly black community patrolled by an overwhelmingly white police force.
Belmar said that unless his agency could bring in 10,000 officers, "I don't think we can prevent folks who really are intent on destroying a community".
Obama said on Monday night from the White House that some Americans might but angry, but need to accept the grand jury's decision.
"We are a nation built on the rule of law, so we need to accept that this decision was the grand jury's to make," Obama said.
He echoed Brown's parents in calling for any protests to be peaceful.
The vast majority of protesters had left the streets by late on Monday, but looting and gunfire still were reported well after midnight.
