President Barack Obama said those who looted and started fires in Baltimore “should be treated like criminals”.
He also said police violence against African-Americans is a “slow-rolling crisis” after a night of violence in Baltimore.
The Baltimore rioting came after the funeral of Freddie Gray, a black man fatally injured in police custody in the city.
A week-long curfew has been announced and thousands of troops have been deployed to Baltimore.
The National Guard has been sent to Baltimore to stop unrest for the first time since 1968, when some of the city’s neighborhoods went up in flames after the assassination of the Reverend Martin Luther King Jr.
About 200 people were arrested on April 27, when more than 100 cars were set alight and 15 buildings destroyed.
Barack Obama harshly criticized “a handful of people” for “senseless violence and destruction”.
“That is not a protest, that is not a statement, they are stealing.”
However, Barack Obama said the rioting had distracted from the frustration over Freddie Gray’s death.
“This has been a slow-rolling crisis. This has been going on for a long time. This is not new. And we shouldn’t pretend that it’s new,” Barack Obama said.
The president added such problems would not be solved just by changes to policing.
“It would require everybody saying this is important, this is significant, and that we don’t just pay attention to these communities when a CVS burns and we don’t just pay attention when a young man gets shot or has his spine snapped.”
At an afternoon briefing, Baltimore Captain Eric Kowalczyk was asked why the police had not responded with more resources to prevent fires and rioting.
Capt. Eric Kowalczyk said police had originally deployed for a “high school event”, expecting young students.
“I don’t think there’s anyone in the country that would expect us to deploy automatic weapons and armored vehicles to an event with 13, 14 and 15 year olds,” but saw it turned into an incident that drew in older troublemakers and escalated in violence.
Out of 235 arrests, 201 were adults, Capt. Eric Kowalczyk said.
He also noted there was a large group at a major intersection in Baltimore on April 28 who were protesting peacefully.
“That’s what we’re used to seeing in Baltimore.”
Volunteers and city workers began cleaning up affected areas on Tuesday morning. Smoke still rose from buildings set alight the night before.
Freddie Gray, 25, died on April 19 after suffering unexplained injuries to his spinal cord and spending a week in a coma.
Officials have suspended six police officers who were involved in the case.