San Diego police broke up a rowdy demonstration Friday afternoon after protesters refused to disperse at the end of a Donald Trump rally.
"Due to violence and physical confrontation in the crowd, officers are now moving into the area. Dispersal orders have been given," the Police Department said on Twitter.
At least 18 people received medical attention, and San Diego police declared an unlawful assembly in the Gaslamp district because of violence about 4:40 p.m., announcing in Spanish and English that people needed to disperse. Officers with riot gear were moving among the crowd.
By 6 p.m. police appeared to have restored order.
Several people were throwing plastic bottles, some of which hit police officers, near Petco Park on L Street between 5th and 6th avenues. Also nearby, a man with a "Make America Great Again" hat took it off and burned it among a crowd.
Several small street fights broke out in the same area as the environment became tense when anti-Trump crowds started to mix with his supporters.
At least three people were arrested.
Trump left the area about 4:30 p.m., but hundreds of anti-Trump demonstrators remained in the downtown area.
During Trump's talk, videos showed some protesters throwing objects at a line of police officers. At least one protester tried to climb up to where the officers were. The video showed officers using batons to push him back into the crowd.
San Diego police said three people were arrested after "several protesters tried to breech a secured area."
Hours earlier, a much smaller group of demonstrators were on hand when Trump spoke in Fresno.
"If I win, believe me, we're going to start opening up the water so that you can have your farmers survive, so that your job market will get better," Trump told a few thousand cheering supporters at Selland Arena.
The presumptive Republican presidential nominee mocked environmentalists for "trying to protect a certain kind of 3-inch fish."
Trump spoke in Fresno for the first of two California rallies and was greeted by supporters and protesters.
Outside the venue, some anti-Trump activists held signs supporting Democratic presidential hopeful Bernie Sanders or waved Mexican flags; others marched down the street and chanted, "Whose streets? Our streets!"
Inside, Trump called for protesters to be escorted out. Police removed about 30 people in one sweep, some of whom held a "Love Thy Neighbor" banner in the upper section of the stands.
"Thank you, you have a beautiful voice," Trump replied to a protester who shouted obscenities his way. "Get 'em out."
Trump touched on familiar topics throughout his speech – building a border wall, his debate ratings, Hillary Clinton's bid for the Democratic nomination – and pushed back against claims that he does not respect women.
"Believe me, I love women," Trump told the crowd. "You know what else? I have great respect for women. With men, I'm setting records. Men like Trump!"
Trump said he will "make a strong play" in California, despite claims that a Republican cannot win the state.
"I am going to make a heavy, heavy, heavy play because I honestly think with getting these massive crowds … we are going to win California," he said.
Anti-Trump demonstrators continued protesting outside after Trump’s speech ended, police said, despite calls from authorities to clear out. Police arrested two people for failure to disperse, according to Fresno Police Chief Jerry Dyer.
In San Diego, Trump's rally drew several hundred protesters to downtown's Gaslamp district, but their access to the convention center across the street was blocked by dozens of police officers.
Janitors from a local union waved mops, moms pushed strollers and Latino activists denounced Trump with pinata effigies and Spanish-language chants.
"El pueblo unido, jamas sera vencido," they yelled: The people united, will never be defeated.
"Speak English," some Trump supporters yelled back.
Pro- and anti-Trump groups traded insults over loudspeakers, but there were no serious incidents before the event.
"Stay classy San Diego," read the sign of Sam Huerta, who wasn't taking sides, but urged everyone to keep the peace.
San Diego Police Chief Shelley Zimmerman had pledged that the city's law enforcement agencies would be able to respond to any sort of incident. The Police Department is familiar with creating plans for all kinds of large gatherings, including Comic-Con and political demonstrations, she said.
"The contingency plan that we have in place here is going to allow for a safe environment, and if anyone chooses to do something otherwise, we're confident that our contingency plan can address those few individuals who don't choose to follow the law," she said.
Others were concerned about whether law and order would be maintained.
"I am concerned; I had heard from a police spokesman that the police have been asked to stand down," said hotel developer Doug Manchester, one of the organizers of the rally and a Trump delegate to the Republican National Convention this summer.
"Why should the demonstrators be allowed to go onto the public streets and demonstrate when it blocks the Hyatt, the Marriott, the Hilton and other businesses downtown?" asked Manchester, the former owner of the San Diego Union-Tribune. "It prevents businesses to do transactions like on a normal basis."
Zimmerman emphatically rejected the notion that any officers were told to stand down during the protests and rally.
Francine Busby, head of the San Diego County Democratic Party, said her group worked to coordinate protests with a coalition of organizations representing Latinos, women, veterans and others.
Tony Krvaric, chairman of the Republican Party of San Diego County, said his organization was not planning a counter-protest.
Unión del Barrio, a political group in San Diego focused on social justice issues facing Latinos, also planned to protest, staging at Chicano Park and marching to the San Diego Convention Center. An organizer, Harry Simón, said five or six other groups have their own anti-Trump events planned.
"We intend to make our disdain and opposition to Mr. Trump very clear," Simón said.
Abcarian reported from Fresno, Marosi from San Diego. Baker and Garrick are reporters for the San Diego Union-Tribune.
5:37 p.m.: Updated with information about San Diego police action.
4 p.m.: Updated with news from San Diego protests.
2:47 p.m.: This article was updated with scenes from the San Diego rally.
1:45 p.m.: This article was updated with information about protesters in San Diego.
12:02 p.m.: This article was updated with information on Trump's speech and protesters outside the arena.
10:34 a.m.: This article was updated with Trump arriving in Fresno.
8 a.m.: This article was updated with additional details about San Diego police plans.