Anti-fascist counter-protestors parade through Sacramento after multiple people were stabbed during a clash between neo-Nazis holding a permitted rally and counter-protestors on Sunday at the state capitol in Sacramento, California, United States, June 26, 2016. [Photo/Agencies]

The Sacramento Fire Department said 10 patients were treated at area hospitals for multiple stabbing and laceration wounds.

None of the injuries were life-threatening and there were no immediate reports of arrests, Granada said. The building was placed on lockdown.

Matthew Heimbach, chairman of Traditionalist Worker Party, said his group had expected violence even though it planned a peaceful rally and had a permit.

"We were there to support nationalism. We are white nationalists," Heimbach told Reuters. "We were there to take a stand."

Representatives of the Sacramento police could not be reached immediately for further comment.

Video footage on social media showed dozens of people, some of them wearing masks and wielding what appeared to be wooden bats, racing across the capitol grounds and attacking others.

Photos on social media showed emergency officials treating a victim on the grass in the area as police officers stood guard.

The melee comes about four months after four people were stabbed during a scuffle between members of the Ku Klux Klan and counter-protesters near a KKK rally in Anaheim, California.

In recent months Trump has blamed "professional agitators" and "thugs" for violence that has broken out at many of the Republican candidate's rallies.

In Albuquerque, New Mexico, last month, anti-Trump protesters threw rocks and bottles at police officers who responded with pepper spray. A month earlier, some 20 demonstrators were arrested outside a Trump rally in Costa Mesa, California.