Five people were taken to hospitals on Sunday after violence broke out between two groups during a rally, according to the Sacramento, California, Fire Department.
The victims had stab wounds that required critical medical care, Chris Harvey, spokesperson for the fire department, told CNN. Their conditions were not immediately known.
He said the brawl broke out around noon when a group of "right-wing extremists" held a planned rally near the state capitol.
"They were met by a large number of counter-protesters," Harvey said. "We had quite a large fight and a number of smaller fights that broke out from that."
Video showed people running and being pursued by others with sticks. Some of the people hid their faces with scarves and masks.
Harvey said he didn't know whether police had arrested anybody.
"It's unclear at this time how much of this was planned and how much of it was sort of a sudden reaction to what was going on here," he said.
By Ralph Ellis