"Now is the time for healing. Now is the time for peace and calm on the streets of Ferguson," the president told reporters in Martha's Vineyard, where he is on vacation with his family. "Now is the time for an open and transparent process to see that justice is done."
The president said he spoke Missouri Gov. Jay Nixon this morning.
"I expressed my concern over the violent turn that events have taken on the ground, and underscored that now's the time for all of us to reflect on what's happened and to find a way to come together going forward," the president said.
This is the first time the president has spoken publicly about events in Ferguson since the Brown, 18, was shot by a still-unnamed police officer. Obama urged restraint by both law enforcement and protesters.
"There is never an excuse for violence against police or for those who would use this tragedy as a cover for vandalism or looting," the president said. "There's also no excuse for police to use excessive force against peaceful protests or to throw protesters in jail for lawfully exercising their First Amendment rights."
Obama also addressed military operations in Iraq, saying air strikes against the terrorist group known as ISIL or ISIS in northern Iraq had already saved many lives.
"Because of the skill and professionalism of our military and the generosity of our people, we broke the ISIL siege of Mount Sinjar, we helped vulnerable people reach safety and we helped save many innocent lives," he said.
Because of the progress, the president said he did not expect there would be a need for an additional military operation to evacuate Iraqi civilians from Mount Sinjar.
But U.S. airstrikes will continue because even as the situation on Mount Sinjar has been has improved, it remains dire elsewhere in Iraq where ISIS remains in control, he said.
Shortly after the president spoke, he arrived at the Vineyard Golf Club in Edgartown for a round of golf.
The president's golf partners today are Cyrus Walker, who is the cousin of Obama's senior adviser Valerie Jarrett, World Bank President Jim Kim, and former U.S. trade representative Ron Kirk.