US President Barack Obama said there is "no excuse" for excessive force by police or those looting and carrying guns in the Missouri town where a teenager was shot by an officer.
He said: "There is no excuse for excessive force by police or any action that denies people the right to protest peacefully. Ours is a nation of laws for the people who live under them and the people who live under them."
He added: "We have all seen images of protesters and law enforcement in the streets. It is clear that the majority are peacefully protesting. It is also clear that a minority are not."
While he accepted that the shooting had raised passions across much of the community he said: "Giving into that anger by looting or carrying guns or even attacking the police, only serves to raise tensions and stir chaos. It undermines rather than advancing justice."
More top news
Rain across much of the remainder of the country
Singer knocks Oasis from their 18-year hold on the top spot as her third album sells more than 800,000 copies in its first week of release
Francois Hollande has urged British MPs to support David Cameron's plan to launch airstrikes against so-called Islamic State in Syria.