Boston police said 27 people were arrested during day-long demonstrations to protest hate speech a week after a woman was killed at a Virginia white supremacist rally. (Reuters)

BOSTON Tens of thousands of counterprotesters crammed Boston Common and marched through city streets Saturday morning in efforts to drown out the planned free speech rally that many feared would be attended by white-supremacist groups.

By 1 p.m., the handful of rally attendees had left the Boston Common pavillion, concluding their event without planned speeches. A victorious cheer went up among the counterprotesters, as many began to leave. Hundreds of othersdancedin circles andsang, Hey hey, ho ho. White supremacy has got to go.

City officials said that at least 40,000 people participated in the counter protest, 20,000 of whom participated in a march across town.Tensions flared as police escorted some rally attendees out of the Common, prompting several physical altercations between police and counterprotesters.

Boston Police Commissioner William Evans said there were 27 arrests, primarily for disorderly conduct. He said no officers or protesters were injured and there was no property damage. Evans added that three individuals were wearing ballistics vests, one of whom was later found to be armed. It is unclear if those three are among the arrests.

Evans said there were three groups of people in attendance: attendees of the free speech rally, counter protesters, and a small group of people who showed up to cause trouble.

Overall everyone did a good job, Evans said. 99.9 percent of people were here for the right reason, and thats to fight bigotry.

Boston Mayor Martin J. Walsh met up with the counterprotesters at themarch.

I think its clear today that Boston stood for peace and love, not bigotry and hate, he said.

[Donald Trump brought me here today: Counterprotesters rout neo-Nazi rally in Berlin]

President Donald Trump praised law enforcement and Mayor Marty Walsh via tweet Saturday afternoon for their handling of the crowds, saying that there appeared to be many anti-police agitators in Boston. More than an hour later, he tweeted support for protesters.

The showdown between right-wing ralliers and the far larger group of counterprotesters in the heart of downtown Boston comes just one week after a chaotic gathering of far-right political groups including neo-Nazis, white supremacists and Ku Klux Klan members left dozens injured and one woman dead in Charlottesville aftera reported neo-Naziallegedly plowed his carinto a crowd of counterprotesters.

In anticipation of potential violence, city officials corralled more than 500 police officers onto the Common, installed security cameras and constructed elaborate barriers to separate the free-speech rally from the massive demonstration in opposition to it. The handful of rally attendees gathered beneath a pavilion near the center of the Common, surrounded by metal barriers and dozens of police. Several hundred feet away, thousands of counterprotesters surrounding them carrying signs declaring Black Lives Matter and Hate Has No Home In Boston, while mockingly chanting we cant hear you when it appeared the ralliers had begun to speak.

One moment of tension came when rally attendees ventured outside of the barriersand were promptly confronted by counterprotesters. One man, draped in a Donald Trump flag, was immediately surrounded by media, while demonstrators chanted at him to go home.

[Shame!: Part of Bostons protest looked eerily like a scene from Game of Thrones]

One rally attendee, Luke St. Onge,a young man wearing a red Make America Great Again hat and GOP T-shirt, saidhe came even though he knew it might be attended by white-supremacist groups, whose views he said he does not agree with.

I definitely wouldnt associate myself with the KKK or any white supremacist. I dont stand with them at all, said St. Onge, who is from Las Vegas. I do support their right to an opinion, he added. Free speech is definitely something I stand for.

Plans for the Boston rally, which organizers said was not about white supremacy or Confederate monuments, were nearly scrapped following the violence in Charlottesville. Several speakerspulled out of or were uninvited from the event, but John Medlar, a Boston-area college student and the rallys lead organizer, said that the rally would go on.

Among those who were scheduled to speak were Joe Biggs, formerly a writer for the conspiracy-theory website Infowars, and Kyle Chapman, a far-right activistcharged with beating counterdemonstratorswith a wooden pole during a clash at the University of California in Berkeley earlier this year, though it is unclear if either man attended. Members of the KKKtold the Boston Heraldthat they expected several of the groups members to attend, but there was little, if any, visible KKK presence at the rally.

There have been questions about why we granted a permit for the rally, Walsh said on Friday. The courts have made it abundantly clear. They have the right to gather, no matter how repugnant their views are. But they dont have the right to create unsafe conditions. They have the right to free speech. In return, they have to respect our city.

Wewill not be offering our platform to racism or bigotry, organizers said in aFacebook postearlier this week. We denounce the politics of supremacy and violence.

Last weeks gathering in Virginia was ostensibly in protest of the proposed removal of a statue of Confederate Gen. Robert E. Lee. In the days since, cities across the nation have announced the removal of dozens of Confederate monuments, sparking anew the long-heated debate over what, if anything, should be done with the hundreds of statutes, streets, and schoolhouses named after or in honor of those who fought to maintain slavery.

[Deconstructing the symbols and slogans spotted in Charlottesville]

Thousands of protesters are expected to attend rallies calling for the removal of Confederate monuments at cities across the country this weekend, including Dallas and New Orleans. Meanwhile, supporters of the Confederate monuments are also organizing, with a rally plannedin Hot Springs, Ark.

Organizers in Boston said todays gathering is not in solidarity with white nationalists, but few of those who attended the massive counterprotest believed them.Across town, thousands began gathering before 10 a.m. on Malcolm X Boulevard for a march to the Common.

Were not standing for it. Were not standing (for) white supremacy. Were not going to have it in our city, not in Boston, said Boston activist Monica Cannon, who was among those who organized the counterprotest. We want to send a clear message that you dont get to come to the city of Boston with your hatred.

Thousands of people demonstrated against a rally featuring right-wing political figures in downtown Boston on Aug. 19. (Claritza Jimenez/The Washington Post)

Rebecca Koskinen stood in front of her brick rowhouse on Tremont Street, awaiting the marchers, with her daughters Elle, 5, and Liv, 1. The older daughters sign read Im only five and even I know Black Lives Matter.

Koskinen said she and her husband, who are white, had taken the girls to the several other marches earlier this year and felt that it was important to show support for an event that was particularly important to people of color especially because Elle will soon start kindergarten at a private school that is less diverse than the South End neighborhood where they live.

Because shes not going to public school, it felt really important to me to talk about this with her and how different groups are treated, Koskinen said.

Joel Moran, a Boston resident who attended the march with his partner and a friend, said he was moved to have my voice heard against white supremacists, against people who think that, for some reason, they have more rights than other people have.

Moran said they were absolutely influenced to participate today after the tragedy in Charlottesville.

It wasnt even on my radar until last weekend, he said. After seeing that and having a very emotional and disturbing response to that, I feel like its basically my responsibility.

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Boston 'free speech' rally ends early amid flood of counterprotesters; 27 people arrested - Washington Post