Tue Aug 11, 2015 3:49AM

Police arrest more than 50 demonstrators who blocked traffic on Interstate 70 outside of Ferguson on August 10, 2015. (AFP photo)
Police arrest more than 50 demonstrators who blocked traffic on Interstate 70 outside of Ferguson on August 10, 2015. (AFP photo)

At least 56 people have been arrested during peaceful protests in St. Louis in the US state of Missouri after police declared a state of emergency.

“This is what democracy looks like,” they chanted as officers were arresting them Monday evening. “If we don’t get no justice, then they don’t get no peace.”

St. Louis County Executive Steve Stenger declared the emergency a day after mayhem in the city on the anniversary of the fatal shooting of unarmed African-American teenager Michael Brown by a white police officer.

"The recent acts of violence will not be tolerated in a community that has worked so tirelessly over the last year to rebuild and become stronger," Stenger said in a statement.

Princeton professor and civil rights activist Cornel West was among several hundred demonstrators who marched to the courthouse from the Christ Church Cathedral on Monday.

 Cornel West was arrested on Monday. (AFP photo) 

The protesters called on the Justice Department to take action against racism in the country.

Video from CNN affiliate KTVI shows protesters holding hands and forming a line in part of Interstate 70 in Earth City, Missouri. Almost 20 minutes later, police cleared the roadway and walked with protesters toward the shoulder, arresting some in a parking lot.

Johnetta Elzie, who has been a mainstay of the demonstrations, tweeted minutes before her arrest, "If I'm arrested today please know I'm not suicidal. I have plenty to live for. I did not resist, I'm just black."

On Sunday night, police clashed with protesters and an African-American man was critically wounded in a gun battle with officers. The man was shot after opening fire on an unmarked police car shortly before midnight.