Police in Baltimore have urged residents to avoid protest areas. Demonstrations over the death of Freddie Gray, 25, turned violent when protesters began throwing objects at police and setting fires in the city.
Rioting broke out in the northwestern corner of the city on Monday afternoon not long after Gray's funeral, which drew over 2,000 people, including White House officials.
At least seven police officers were injured in the clashes, with one reported as unresponsive.
Police spokesman Eric Kowalczyk characterized the demonstrators as a "group of lawless individuals with no regard for the safety of people who live in that community."
They were a "large group of people spread out over a significant area," he told reporters, adding that police would soon be responding with tear gas.
Local television broadcaster WBAL showed scenes of looting on the streets, with dozens of men and women storming a liqour store and a CVS pharmacy, which was set on fire. CVS says no employees were injured.
Maryland's National Guard was put on alert by the state governor, Larry Hogan.
US broadcaster ABC tweeted a statement from the Baltimore police urging local residents to take precautions in order to avoid the violent crowd.
Protesters threw bottles, bricks and other heavy object at police. They also set at least one police vehicle on fire, as seen in this tweet from US daily The Washington Post.
Several local businesses and the University of Maryland's main campus shut down in response to the unrest on Monday.
At least 34 people have been arrested since protests began last week.
Pastor: 'This was a sacred day'
Family, friends and supporters of the movement to uncover the cause of Gray's death at police hands gathered on Monday to pay their respects. Among them were at least two White House officials and the mayor of Baltimore, Stephanie Rawlings-Blake.
News of violence following the burial prompted a sharp response from the pastor who delivered Gray's eulogy.
"This is not what the family asked for today of all days," Reverend Jamal Bryant said, according to news agency DPA.
"This was a day of sacred closure."
Protesters calling for justice
Gray died on April 19 after sustaining a fatal injury in police custody.
On Friday, Baltimore Police Commissioner Anthony Batts said officers had failed to give Gray timely medical attention for the spinal injury he suffered while in their custody. With his death, the 25-year-old joined a long list of black men killed under questionable circumstances during police encounters and became at least the fifth black man to die in police encounters in Baltimore since Batts took charge.
The Baltimore protests are the latest in a series of demonstrations across the US following African American men's deaths under questionable circumstance during police encounters, including Michael Brown by a white officer in Ferguson, Missouri, Eric Garner in New York City, and Walter Scott in Charleston, South Carolina.
kms/gsw (AFP, Reuters, dpa)