FERGUSON, Mo. — The Missouri Highway Patrol seized control of a St. Louis suburb Thursday, stripping local police of their law-enforcement authority after four days of clashes between officers in riot gear and furious crowds protesting the death of an unarmed black teen shot by an officer.

The intervention, ordered by Missouri Gov. Jay Nixon, came as President Barack Obama spoke publicly for the first time about Saturday’s fatal shooting of Michael Brown and the subsequent violence that shocked the nation and threatened to tear apart Ferguson, a town that is nearly 70 percent black patrolled by a nearly all-white police force.

Obama said there was “no excuse” for violence either against the police or by officers against peaceful protesters.

Nixon’s promise to ease the deep racial tensions was swiftly put to the test as demonstrators gathered again Thursday evening in the neighborhood where looters smashed and burned businesses on Sunday and police repeatedly fired tear gas and smoke bombs.

But the latest protests were a world apart from the earlier demonstrations, with a light, even festive atmosphere and no hint of violence. The streets were filled with music, free food and even laughter.

Protester Cleo Willis said the change was palpable.

“You can feel it. You can see it,” he said. “Now it’s up to us to ride that feeling.”