(CNN) Thousands of counterdemonstrators marched Saturday in downtown Boston in a largely peaceful response to a self-described free speech rally that had sparked concerns of possible violence.

The march and rally came one week after racially motivated protests in Charlottesville, Virginia, turned deadly. There were no major incidents reported Saturday in Boston, but police said 33 were arrested -- mostly for disorderly conduct and assaults on police officers.

"It's clear today that Boston stood for peace and love, not bigotry and hate," Boston Mayor Marty Walsh said.

Amid a heavy police presence, men, women and children from diverse backgrounds showed up Saturday morning to march from the Reggie Lewis Track and Athletic Center in Roxbury to Boston Common, the nation's oldest park.

A woman is detained Saturday as officers escort police wagons away from Boston Common.

#BlackLivesMatter organized march started in Boston against racism & Alt-light rally at #BostonCommon & in solidarity w #Charlottesville. pic.twitter.com/hEljI0lyxG — Sara Sidner (@sarasidnerCNN) August 19, 2017

A coalition of mostly left-leaning groups and activists such as the Black Lives Matter movement organized Boston's counterprotest.

Some carried signs with messages such as "No Trump. No KKK. No racist USA" and "Americans against hate." At times, they chanted "Hey hey, ho ho, white supremacy has got to go" and "Black lives matter."

"Boston is a beautiful city, but Boston needs to get it together," counterdemonstrator Lewis Goody said. "It has always been a racist city."

Police maintained a buffer zone between marchers and rally participants -- averting major incidents except for occasional clashes and shouting matches between the counterprotesters and supporters of President Donald Trump.

Trump, widely criticized after pointing to "blame on both sides" in Charlottesville, tweeted Saturday that there appeared to be "many anti-police agitators" in Boston but later praised protesters for "speaking out against bigotry and hate."

I want to applaud the many protestors in Boston who are speaking out against bigotry and hate. Our country will soon come together as one! — Donald J. Trump (@realDonaldTrump) August 19, 2017

Rally ends earlier than expected

The rally began at noon on Boston Common, and by 1:30 p.m., police tweeted: "'Free Speech' rally is officially over. Demonstrators have left the Common."

#UPDATE: "Free Speech" rally is officially over. Demonstrators have left the Common. — Boston Police Dept. (@bostonpolice) August 19, 2017

Around the same time, helmeted police officers could be seen on news footage moving in to separate rally participants from counterdemonstrators. The event had been scheduled to end at 2 p.m.

A counterprotester, left, confronts a professed Trump supporter Saturday on Boston Common.

Police Commissioner William Evans said the boisterous marchers far outnumbered the rally participants. Many of the latter were escorted out in police vans to keep them away from counterprotesters. Clashes erupted when platoons of officers came in to disperse the crowds.

"We didn't want what happened in Virginia to happen here," Evans said. "We didn't want them at each other's throats."

Shortly after 3:30 p.m. -- when many downtown thoroughfares had started to reopen even as pockets of counterdemonstrators remained on the streets -- Boston police via Twitter asked people to stop throwing "urine, bottles and other harmful projectiles at our officers." Police also said rocks were thrown at officers.

#UPDATE: #BPD confirming rocks being thrown at officers on Tremont at West. — Boston Police Dept. (@bostonpolice) August 19, 2017

The event, which was planned before the Charlottesville violence, took place amid a heated national debate about racism and the future of Confederate monuments.

Counterprotesters hold signs as they prepare to march against the self-described free-speech rally.

Smaller protests were expected in cities throughout the nation.

In Hot Springs, Arkansas, a pro-Confederate rally was held Saturday amid heightened security concerns following the clashes in Virginia.

Josie Fernandez, superintendent of Hot Springs National Park, described the event as largely peaceful. She said that 300 rally participants and counterprotesters attended and that local police had made two arrests.

In Portland, Oregon, hundreds took to the streets Friday night for an "Eclipse Hate" demonstration, which organizers said was intended to show solidarity with the people of Charlottesville, CNN affiliate KPTV reported. The event included a moment of silence for victims of hate.

There were also gatherings in Atlanta; Austin, Texas; Dallas; Durham, North Carolina; New Orleans and other cities, with similar themes.

Throngs march before the start of Saturday's rally in downtown Boston.

Rally organizers in Boston had invited "libertarians, conservatives, traditionalists, classical liberals, Trump supporters or anyone else who enjoys their right to free speech," according to a group calling itself the Boston Free Speech Coalition.

Boston Mayor Marty Walsh had appealed for calm via Twitter earlier Saturday: "I ask everyone to be peaceful today and respect our City. Love, not hate. We stand together against intolerance."

I ask everyone to be peaceful today and respect our City. Love, not hate. We stand together against intolerance. — Mayor Marty Walsh (@marty_walsh) August 19, 2017

After Boston granted a rally permit this week, Walsh had issued a warning to the demonstrators: "Make no mistake: we do not welcome any hate groups to Boston and we reject their message."

"We have made it clear that we will not tolerate incitements to violence or any threatening behavior."

Counterprotesters turn out Saturday at the Massachusetts Statehouse opposite Boston Common.

Boston rally organizer denounces 'political violence'

A Facebook page linked to the Boston event identifies participants as a "coalition of libertarians, progressives, conservatives, and independents and we welcome all individuals and organizations from any political affiliations that are willing to peaceably engage in open dialogue about the threats to, and importance of, free speech and civil liberties."

Some of the same groups organized a similar event on the Common in May, where there were two arrests.

One organizer, John Medlar, a student at Fitchburg State University, told CNN affiliate WCVB that his group is libertarian and opposes bigotry and the Ku Klux Klan.

Medlar also told CNN affiliate WBZ , "Contrary to a lot of the rumors out there, the purpose of the rally is to denounce the kind of political violence that we have seen -- a sort of rising tide throughout the country, and particularly most recently in Charlottesville."

The Anti-Defamation League said the Boston rally, as planned, is not a white supremacist event.

"It has been organized under the auspices of the alt lite, which embraces civic nationalism, rather than the alt right, which advocates white nationalism," the ADL said in a blog post

"The alt lite, sometimes referred to as the New Right, is a loosely-connected movement whose adherents generally shun white supremacist thinking, but who are in step with the alt right in their hatred of feminists and immigrants, among others. Many within the alt lite sphere are virulently anti-Muslim; the group abhors everyone on 'the left' and traffics in conspiracy theories."

Controversial speakers

Some speakers had dropped out, while others were uninvited after Charlottesville. But rally organizers said on social media that Kyle Chapman, Joe Biggs, US Senate candidate Shiva Ayyadurai and congressional candidate Samson Racioppi were to speak.

Chapman and Biggs are probably the most controversial.

Chapman is well-known in right-wing circles for arming himself with a stick and confronting anti-fascist demonstrators in Berkeley, California, according to the ADL. Known by the nickname Based Stickman or the Alt Knight, he has urged members of his group to battle left-wing activists, the ADL said.

Biggs, a former contributor to Alex Jones' InfoWars , is chief operations officer at the online outlet Rogue Right Media.

The counterdemonstration was organized by an array of groups, including the Coalition to Mobilize and Organize Boston against Trump, the Act Now to Stop War & End Racism Coalition, Boston Democratic Socialists of America and Black Lives Matter, according to a Facebook page for the event.

JUST WATCHED Video shows what happened in Charlottesville Replay More Videos ... MUST WATCH Video shows what happened in Charlottesville 02:59

"As we have seen with the events in Charlottesville and around the country, white nationalists are emboldened by the current political administration and growing police state," organizers wrote on Facebook.

"Rallies and marches organized by white supremacists are more prevalent than in recent years, and -- as always -- it is the most marginalized who are left vulnerable."

Monica Cannon, an organizer with the group Violence in Boston, said activists who participated in last week's Charlottesville event were to attend.

Boston prepared, city officials vow

Boston officials said before the rally that the city was prepared.

More than 500 police officers -- including some undercover and others with cameras -- were to be on hand.

Backpacks were to be searched and weapons, and objects that could be used as weapons -- including glass containers and flag poles -- were to be banned.

Boston Mayor Martin Walsh says his city is prepared should violence break out at Saturday's rally.

"If anything gets out of hand, we will shut it down," Walsh told reporters Friday.

Walsh said the city had no choice but to issue a rally permit.

"The courts have made it abundantly clear they have a right to gather no matter how repugnant their views are," he said.