Police in Anaheim, California, braced for protests at a Donald Trump rally on Wednesday, a day after violence broke out at an event for the presumptive Republican presidential nominee in New Mexico.
Hundreds of protesters tried to swarm the convention center in Albuquerque, New Mexico, where Trump spoke on Tuesday, knocking down barricades and hurling rocks and bottles at police officers dressed in riot gear.
Police said they made arrests both outside and inside the rally, where protesters continually interrupted the billionaire New York developer's speech. The police department's Twitter feed said officers were treated for injuries caused by thrown rocks.
Outside the center, demonstrators chanted anti-Trump slogans and waved Mexican flags before they began climbing atop police cars and throwing objects. Police responded with smoke bombs and pepper spray.
In a Twitter post on Wednesday, Trump called the protesters "thugs who were flying the Mexican flag."
"The rally inside was big and beautiful, but outside, criminals!" he said.
In Anaheim, where Trump was scheduled to speak at 3 p.m. EDT (1900 GMT) at the city's 7,500-seat convention center, authorities boosted staffing levels, deployed officers on motorcycles to control traffic and urged attendees to be on their best behavior, Anaheim Police Sergeant Daron Wyatt said.
"We respect the rights of everyone to protest and get their word out," Wyatt said, adding they must do so "peacefully and within the confines of the law."
"If they choose not to, we're prepared to take swift and decisive enforcement action," he said.
Clashes between Trump's fervent supporters and rowdy protesters have marked many of his campaign appearances. The violence could prove a hindrance to his efforts to mend divisions within the Republican Party and reach a broader section of the American electorate ahead of the Nov. 8 election in which he is likely to face Democratic front-runner Hillary Clinton.
Seventeen people were arrested last month at a Trump rally in Costa Mesa, about 20 miles (32 km) south of Anaheim, media reports said, after protesters blocked traffic and threw rocks and debris at motorists and police officers.