Protesters -- some of whom wore bandanas over their faces and carried Mexican flags -- blocked off the road in front of the Hyatt Regency here, forcing the GOP front-runner's motorcade to pull over along a concrete median outside the hotel's back entrance. Trump and his entourage got out and walked into the building.
At one point, about two dozen protesters tried to rush barriers near the hotel. Police officers then rushed to the building's doors, successfully blocking the protesters from getting in.
Several physical altercations, including shoving, could be seen between protesters and police officers, who were using batons to push them back.
After Trump arrived, protesters took down a barrier and flooded the entrance outside the hotel, where police again blocked them from entering. They chanted, "Get him out."
Protesters have disrupted Trump's rallies across the country for months, but have rarely escalated into mass street demonstrations.
Earlier Friday, bare-breasted protesters, men and women, some of whom were associated with the progressive group Code Pink, chanted "Stop hate" as they marched.
Nancy Mancias, a Code Pink protester, was kicked out of the convention after yelling into a bullhorn that the Republicans should "dump Trump," causing a stir inside the already energized state convention.
Mancias told CNN afterward, "My message here today is 'Stop hate and dump Trump.'"
At one point, a Trump impersonator who supports the GOP front-runner was quickly surrounded by protesters. Police, apparently concerned for his safety, eventually pulled him over hedges outside the hotel and away from the crowd.
About 20 people were arrested Thursday night, police said.
CNN's Eugene Scott contributed to this report.
