Animal rights protesters jumped barricades at a Bernie Sanders rally late Monday in Oakland, California, accusing the candidate of falling short in his efforts to fight "factory farming."

The Democratic presidential hopeful was addressing supporters at Frank Ogawa Plaza at City Hall when five people in their 20s and 30s hopped over barricades and attempted to rush the podium before Secret Service agents escorted them away. Agents also surrounded Sanders.

The group identified itself as the Bay Area-based "Direct Action Everywhere," or DXE. Spokesman Zachary Groff, 24, said "roughly two dozen members of the animal liberation network" were present at the rally.

The group claims to have participated in demonstrations in 152 cities worldwide, including at least four other Sanders rallies.

Groff identified the five group members as Ashley Johnson, of New York City; Rebecca Muniz, of Berkeley; Matt Johnson, of Iowa; Aidan Cook, of Denver; and Amy Halpern-Laff, of Berkeley. They were detained for an hour or two, Groff said, and released without charge.

Video appears to show a Secret Service agent striking one of the barricade jumpers several times with a night stick. Groff identified that person as Johnson, whom he said suffered a bloody wound on his hand.

Although Sanders is, in many ways, the most progressive candidate campaigning, the group says he is not progressive enough when it comes to animal issues.

"Sanders claims to oppose 'factory farming,' but what he hides is that virtually all farms in the United States, including farms he supports, are essentially factory farms," said Groff, a Yale University graduate who is moving to Berkeley. "This was a success. We got the whole country talking about animal rights. You can't really be progressive and oppose animal rights."

Protesters jumped barricades and interrupted a Bernie Sanders rally late Monday in Oakland. Pete Suratos reports.

Activists were not protesting Sanders himself, Groff said, but were trying to pull him in a more progressive direction. The group gave Hillary Clinton higher marks for releasing a campaign platform on animal issues, although the Democratic front-runner also "stops far short of what activists would like to see," Groff said.

Activists said they expect Sanders, "the progressive candidate, to support more radical action to provide animals not just with improved conditions but with legal rights to be free from harm."

The brief scuffle didn't seem to deter Sanders.

"We don't get intimidated easily," the candidate said afterward.

The crowd of about 20,000 was otherwise mostly peaceful. They cheered when Sanders donned a Golden State Warriors cap and told the crowd why he would be the best option for Democrats come November.

"In virtually every state and national poll, we do much better than Trump than Secretary Clinton does," he said.

But Sanders faces an uphill battle, as his Democratic opponent Hillary Clinton is about 70 delegates away from clinching the nomination. A large number of those are superdelegates who could change their minds, and that's what Sanders and his supporters are banking on. Sanders believes a win in California, a state with 475 delegates, would be a giant first step in the right direction.

"If there is a large voter turnout, we will win and win big," he told the gathering in Oakland.

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Supporters aren't giving up either.

"He should stay in to the very last minute," said Joshua Harris, who was at the Oakland rally. "He should stay in as long as he can."

Another Sanders supporter, Jeff Nibert, agreed: "If California can send a message to the country next Tuesday, that would be a shocker around the world."