Explosions echoed and flashes ignited as police fired tear gas to disperse a crowd of about 1,000 people. A huge acrid cloud of tear gas fogged the streets as protesters fled.
One woman, in a wheelchair, could not escape and was among those gassed.
And a reporter for KRON 4, Jeff Bush, could not continue to broadcast because of the sting of tear gas in his eyes.
An injured protester, said to be a U.S. Marine Corps vet, was carried out of the battle zone in Oakland, California, during a night of violent clashes. He was reportedly hit in the head by a tear gas grenade.
The protests in Oakland, and in Dallas, Boston, and other cities across America all began with the Occupy Wall Street movement. So far, New York City is allowing these protesters to continue to camp in Zuccotti Park. But other cities are closely watching what happens in Oakland and may also be preparing to take a tougher stand.
There were more than 100 arrests as the Oakland protestors tried to reclaim a downtown park where police had evicted them after a two-week occupation.
INSIDE EDITION producer Daela Cetrone reported from the scene.
"It's a quiter scene in Oakland today. City workers are working diligently to clean up the mess from last night. They're spraying down the sidewalks. They're cleaning up the graffiti. And police have erected steel barricades to keep the protesters out. They say they're ready with their batons, their guns, their riot gear. Protesters have also decorated the steel barricades. They say this is not going to stop them at all," said Cetrone.
Police said they were forced to use tear gas only after officers were struck with paintballs and other missiles.