Police deploy gas and pepper spray to disperse protesters outside Trump rally as thousands gather

'People in the crowd have begun throwing rocks and bottles,' says police spokesman

Police outside the Phoenix Convention Centre (Matt York/AP)

Police deployed gas to disperse crowds in Phoenix, Arizona, after protesters outside a rally by US President Donald Trump threw rocks and bottles, police said.

“People in the crowd have begun throwing rocks and bottles at police. They also dispersed some gas in the area,” Phoenix Police Department spokesman Sergeant Jonathan Howard said.

“Police have responded with pepper balls and OC (oleoresin capsicum) spray in an attempt to disperse the crowd and stop the assaults,” he said.

Police have not given an estimate of the number of protesters who turned out for the event, but Arizona media said there were several thousand people.

Media reports said some protesters had thrown bottles at police.

Earlier, minor scuffles and shouting matches erupted between protesters and Mr Trump's supporters, with authorities on high alert as thousands of people lined up in the triple-digit heat to attend his first political rally since the violence in Charlottesville, Virginia.

The scene was noisy, but largely peaceful as Phoenix police kept most members of the two opposing groups behind barricades and apart on separate sides of the street. As a police helicopter hovered overhead, officers wearing riot gear and carrying rifles sauntered through the lane between the sides. Authorities said no one was arrested, though a few were treated for heat exhaustion.

Local authorities were vigilant in the aftermath of the deadly protests in Virginia and the president's comments last week about both sides having blame for violence at the white supremacist rally. Mayor Greg Stanton had unsuccessfully called on the president to not hold the rally here so soon after the trouble in Charlottesville.

“Toxic Trump,” read one protest sign held up to the president's supporters streaming into the Phoenix Convention Centre downtown. “Lock Him Up!” read another, a reference to earlier campaign chants by Trump and his backers about his election rival Hillary Clinton.

Dillon Scott of Phoenix, who voted for Clinton, said he came out to express dissatisfaction with how long Trump took to denounce racism after the Charlottesville violence.

“No one should be allowed to get away with what he gets away with, especially in political office,” Mr Scott said.

Meanwhile, a group of protesters chanted, “Wrong side of history! Wrong side of history!”

Trump backer Randy Hutson, a retired Phoenix police officer, began standing in line more than seven hours before the speech was to start. “He is the first president I feel in my lifetime that speaks his mind and speaks from the heart,” Mr Hutson said. “He says what needs to be said.”

Three Trump supporters taunted Latino protesters with offensive comments about immigrants and held anti-Muslim and Black Lives Matter signs.

As the line to get in the venue moved ahead, the two groups shouted at each other and some skirmishes broke out. At one point, a Trump supporter and protester shoved each other.

John Brown, of an anti-Trump group calling itself the Redneck Revolt, wore military fatigues and had an AK-47 rifle strapped to his chest as he and a half dozen others from the group stood about 30 feet behind the barricade for protesters. He said they were there to protect Trump opponents and stand up to fascism. “He's offensive to me in every way,” Mr Brown said.

Reuters and Associated Press