BURLINGAME (AFP) -- Hundreds of demonstrators jostled with police in riot gear outside a California hotel where Republican presidential frontrunner Donald Trump gave a speech, forcing the candidate to duck into a back entrance.

At one point, several dozen protesters broke through barricades and attempted to storm the hotel where the California Republican Party Convention was taking place on Friday, but police, some wielding batons, were able to push them back.

The demonstrators waved banners that read "No hate, no racism, no Trump,"  "We need a uniter, not a divider" and "Trump is the modern day Hitler." Several carried Mexican flags.

The tense stand-off at the Hyatt Regency near the San Francisco International Airport forced the Republican front-runner and his security detail to abandon his motorcade on a nearby highway, hop over a barrier and use a back entrance to the hotel.

"That was not the easiest entrance I've ever made," he told the party members at the convention. "It felt like I was crossing the border."

California, which holds its presidential primaries on June 7, is crucial in Trump's push to secure the number of delegates needed to win the Republican presidential nomination outright.

Trump blasted his rivals Texas Senator Ted Cruz and Ohio Governor John Kasich for staying in the race.

"I think it's going to come to an end very soon," Trump told the crowd. "And really, I'm speaking to the people in this room, because there has to be unity in our party."

After delivering his speech without incident, Trump was again escorted out the back entrance.

A crowd of those attending the convention watched live footage of Trump leaving the hotel, and cheered when he entered his vehicle away from the protesters, the Los Angeles Times reported.

Kasich, who hours later spoke to the California Republicans, did not refer directly to Trump but did say that he's chosen in his own campaign "not to live on the dark side of human nature."

Once seen as inconceivable, Trump's quest for the 1,237 delegates needed to win the Republican nomination outright is within reach.

Some of the anti-Trump protesters outside the hotel lobbed rocks and eggs at officers, and at least five were arrested, a police spokesman said.

He added that several demonstrators and police officers suffered minor injuries.

"I am here because I don't like all the bad stuff Trump has been saying lately about immigrants and Latinos," said Eric Lopez, one of the demonstrators. "We are not all like the way he thinks we are."

Jorge-Mario Cabrera, spokesman for the Coalition for Humane Immigrant Rights of Los Angeles (CHIRLA), denounced Trump's rhetoric and said he hoped the real estate magnate would be defeated at the polls.

"The community is sick of being denigrated, disrespected and attacked," he told AFP in a statement. "Nevertheless, our reaction should be to march peacefully, as we have always done, and vote at the polls."

The protest in Burlingame followed similar demonstrations that turned violent late Thursday at another Trump rally in southern California.

Some 20 people were arrested outside the Orange County amphitheater in Costa Mesa during a Trump campaign stopover, which drew a crowd of thousands ahead of the state's June 7 primary.

The demonstrators hurled rocks at passing vehicles and vandalized cars. They smashed at least one patrol car's window and punctured the tires on a police sports utility vehicle, while trying to overturn another police car.

Protesters have disrupted campaign rallies for Trump across the country, denouncing the frontrunner's rhetoric against Muslims and immigrants.

The billionaire developer has outraged many by comparing Mexican immigrants to "rapists" and vowing to build a wall along the Mexican-American border to prevent illegal immigration.