Jay Nixon also said a curfew would run from midnight local time until 05:00 AM in Ferguson.
The move comes after a week of violent clashes between heavily armed local police and protesters.
Michael Brown, 18, was shot dead on a street in Ferguson on August 9.
Governor Jay Nixon said that although many protesters were making themselves heard peacefully, he would not allow a handful of looters to endanger the community.
“We must first have and maintain peace. This is a test. The eyes of the world are watching,” he said.
“We cannot allow the ill will of the few to undermine the good will of the many.”
Jay Nixon also said the Department of Justice was bolstering its investigation of the shooting.
Missouri State Highway Patrol Captain Ron Johnson, who is in charge of security in Ferguson, said 40 FBI agents were going door-to-door to gather information about the incident.
Ron Johnson gave a joint press conference with Governor Nixon at a church in Ferguson, where they were repeatedly interrupted by angry locals.
On Friday, police released CCTV footage that it said showed Michael Brown stealing from a convenience store and intimidating its owner.
Michael Brown’s family said they were “beyond outraged” by the video, criticizing what they said was a police attempt to “justify the execution-style murder”.
Police later said that the officer who shot Michael Brown did not know he was a robbery suspect.
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