Following a fourth night of racially charged demonstrations in Ferguson, Missouri, during which police fired tear gas and smoke bombs to disperse crowds of protesters, President Obama urged Americans to unite under the United States’ common values.

“Now’s the time for healing, now’s the time for peace and calm on the streets of Ferguson,” Obama said Thursday afternoon during a televised appearance in Martha's Vineyard.

He added that “we all need to hold ourselves to a higher standard, particularly those in a position of authority.”

Police in Ferguson fired tear gas, stun grenades and smoke bombs to disperse several hundred protesters late Wednesday as they railed against the death of an unarmed black teenager who was shot by police.

Protesters have gathered every night since Saturday when 18-year-old Michael Brown was killed by police in the mostly black suburb of St. Louis. Witnesses said Brown had his hands raised in the air at the time of the shooting, while police said there was a struggle over a gun in the police car.

At least 10 protesters were arrested overnight, the St. Louis Post-Dispatch reported. At least 50 have been arrested since Saturday.

“I’ve had enough of being pushed around because of the color of my skin. I’m sick of this police brutality,” one protester, who only gave his first name, Terrell, said. “I’m going to keep coming back here night after night until we get justice.”

Obama said Thursday that the Department of Justice was consulting with local authorities in Ferguson “to maintain public safety without restricting peaceful protests” or engaging in “unnecessary escalation.”

He said that protesters had no excuse for using violence against police or looting, and that police also had no excuse for throwing protesters in jail.

The president also criticized police for their treatment of two journalists who were detained by police on Wednesday. Police “should not be bullying or arresting journalists who are just trying to do their jobs,” Obama said.

Missouri Gov. Jay Nixon also spoke Thursday afternoon, stressing the importance of safety as protesters expressed their anger and frustration.

"We've got to use this energy and not use it as an excuse to spin off, but use it to push forward," he said.

"If news media wants to cover stuff, and take pictures of stuff, they ought to do it. We live in a free country," he added.