More than 20 protesters parked cars in the middle of a road leading to a Trump rally at Fountain Hill, Arizona. In New York, a thousand demonstrators gathered outside Trump Tower to denounce his campaign.
Protesters blocked a main highway on Saturday leading into a Phoenix, Arizona suburb where Republican presidential front-runner Donald Trump held a campaign rally.
About two dozen people blocked the road, unfurling banners with the words "Dump Trump" and Must Stop Trump."
They then marched to the rally site, amid anger from Trump supporters who booed and jeered them. Three people were arrested, police said.
In a speech to followers, Trump reiterated his pledge to rebuild the military and build a border wall with Mexico. He drew cheers from the crowd when he vowed to protect the Second Amendment of the US Constitution which guarantees the right to bear arms.
Later at another rally in Tucson, Arizona, Trump said the protests in Fountain Hill were "disgraceful," and thanked police. He also vowed to act presidential if he is elected to the White House.
Trump was in Arizona ahead of Tuesday's primary, which analysts said he is likely to win. Polls suggest his tough line on immigration has won him the support of many Republican voters.
According to a Real Clear Politics polling average, Trump leads his nearest rival Senator Ted Cruz of Texas by 13 percentage points.
Also on Saturday, protesters rallied outside of Trump Tower in New York to voice their opposition to the billionaire's campaign for the White House.
The crowd of mostly young people carried placards denouncing the real estate magnate, chanting: "Donald Trump, go away, racist, sexist, anti-gay."
Some said police used pepper spray on them as they marched from the park. At least one person was arrested.
Trump rallies have grown increasingly unruly as the months-long campaign has progressed. An event in Chicago a week ago was canceled after protesters swarmed the venue.
Last weekend, a man was arrested when he attempted to rush the stage where Trump was addressing a rally in Ohio.
In another incident, a man who was caught on video punching an anti-Trump protester in the face at a North Carolina rally was arrested and charged with assault.
mm/bw (AFP, AP, Reuters)