Demonstrators took to the streets across the country for a second day on Thursday to protest the Republican presidential election victory of real estate mogul Donald Trump, voicing fears that his triumph would strike a blow against civil rights.

Beefing up protection for two of Trump's marquee properties that have become protest rallying points, police erected security fences around his newly opened Pennsylvania Avenue hotel in Washington and placed concrete blocks in front of the high-rise Trump Tower in Manhattan.

​Trump's critics have expressed concern that his often-inflammatory campaign rhetoric about immigrants, Muslims, women and others — combined with support he has drawn from the Ku Klux Klan and other white supremacists — could spark a wave of intolerance against various minorities.

Anti-Trump rallies were held in more than a dozen major U.S. cities on Wednesday, with thousands turning out for each of the biggest gatherings — in New York, Los Angeles and Oakland, California. In Oakland, unruly protesters smashed windows, set fires and clashed with riot police.

On Thursday, protests emerged in Philadelphia, Baltimore, Grand Rapids, Mich., New York, San Francisco, Los Angeles.

High-spirited high school students marched through San Francisco's downtown, chanting "not my president" and holding signs urging a Donald Trump eviction. They waved rainbow banners and Mexican flags, as bystanders in the heavily Democratic city high-fived the marchers from the sidelines.

"As a white, queer person, we need unity with people of colour, we need to stand up," said Claire Bye, a 15-year-old sophomore at Academy High School. "I'm fighting for my rights as an LGBTQ person. I'm fighting for the rights of brown people, black people, Muslim people."

About 100 protesters marched from the White House, where Trump had his first transition meeting with President Barack Obama on Thursday, to the nearby Trump International Hotel, chanting "love Trumps hate."

A group of protesters gather outside of the White House after U.S. President-elect Donald Trump met with U.S. President Barack Obama at White House in Washington on Thursday. (Carlos Barria/Reuters)

"This generation deserves better than Donald Trump," said Lily Morton, 17, marching with about 100 classmates from the Georgetown Day School. "The queer people, coloured people, women, girls, everyone that is going to be affected by this, we need to protest to help them. There is still love in this country."

Rudy Giuliani, the former New York City mayor and a high-profile Trump supporter, called the demonstrators "a bunch of spoiled cry-babies," in an interview with Fox News.

A bunch of spoiled cry-babies. - Rudy Giuliani, referring to the protesters

Protesters cited a list of objections to Trump, including his campaign rhetoric critical of immigrants and Muslims, as well as allegations that he had sexually abused women and bragged about it. Trump has denied those allegations.

More than 20 people were arrested for blocking or attempting to block highways in Richmond, Va., early Thursday morning.

L.A. mayor praises peaceful protests

Los Angeles Mayor Eric Garcetti has condemned anti-Trump demonstrators who damaged property and blocked traffic. But he says he's proud of the thousands who took to streets peacefully.

The mayor, a Democrat and son of immigrants, said Thursday that had he been younger, he might have hit the bricks as well and called Wednesday's peaceful demonstrations "a beautiful expression of democracy."

On Thursday, a few dozen people again blocked a local freeway in the Boyle Heights area. California Highway Patrol officers were talking to them.

Garcetti said he believed the election of a Republican won't affect federal funding for Los Angeles and said he hoped Trump will set an example and repair damage from his campaign rhetoric, which was seen as virulently anti-immigrant.

Demonstrators gather to protest following Trump's election victory in Manhattan on Thursday. (Lucas Jackson/Reuters)

White House spokesman Joshua Earnest said Obama supported the demonstrators' right to express themselves peacefully.

Republican National Committee spokesman Sean Spicer urged the protesters to give Trump a chance once he is sworn into office in January.

"I hope that people get it out of their — they exercise ... their right to free speech, but then they give this man that was just elected very historically and his new vice president an opportunity to govern," Spicer said in an interview on MSNBC.

Several hundred students at Texas State University in San Marcos took to the campus to protest Trump's election, with many saying they fear he will infringe the civil rights of minorities and the LGBT community.

Civil rights groups and police reported an uptick in attacks on members of minority groups, in some cases carried out by people claiming to support Trump.

There were also reports of Trump opponents lashing out violently against people carrying signs indicating support for Trump.

Police at the university want to know who is behind fliers posted on campus that urge formation of "tar and feather vigilante squads" to "arrest and torture" campus diversity advocates.

The fliers posted around the Texas State University campus Thursday morning featured a picture of armed white men labelled "Texas State Vigilantes" beneath a U.S. flag. It professes support for Trump and Republican majorities in Congress. Aside from the acts against diversity advocates, the flier also urges augmenting a border wall by irradiation with nuclear waste and stocking the Rio Grande with alligators and piranhas. It also urges the sabotage of campus toilets.

Campus police Sgt. Rolando Belmares says at least five fliers were posted around the San Marcos campus before a campus anti-Trump demonstration.

#NotMyPresident

Organizers used social media to plan and schedule many of the protests. A Facebook group using the name "#NotMyPresident," formed by college and high school students, called for an anti-Trump rally on Inauguration Day, Jan. 20.

A protester holds a sign during a protest against Trump's election outside Trump International Hotel and Tower in Chicago Wednesday evening. (Kamil Krzacznski/Reuters)

In New York's Washington Square park, several hundred people gathered to protest Trump's election.

Five kilometres to the north at the Trump Tower on Fifth Avenue, where Trump lives, 29-year-old Alex Conway stood holding a sign with the "not my president" slogan.

"This sign is not to say he isn't the president of the United States, but for two days I can use my emotion to be against this outcome and to express that he's not mine," said Conway, who works in the film industry.

About a hundred protesters gathered at Union Square in Manhattan to protest. They held signs that read "Divided States of America" and "Not My President" and "Let the New Generation Speak!!"

At a subway station along 14th Street, New Yorkers expressed their thoughts — "Time to Fight Back" and "Keep the Faith! Our work is just beginning!" — along the walls of a walkway using sticky notes.

More anti-Trump demonstrations are planned heading into the weekend.

A young woman holds a sign while marching in protest to the election of Republican Donald Trump as President of the United States in Berkeley, Calif., on Wednesday. (Elijah Nouvelage/Reuters)

The United States has seen waves of large-scale, sometimes violent protests in the past few years.

Cities from Ferguson, Missouri, to Chicago have been rocked by demonstrations following high-profile police killings of unarmed black men and teens. Those followed a wave of large-scale protest encampments, starting with the Occupy Wall Street movement in New York in 2011.

Trump said in his victory speech, which was delivered in a far calmer manner than he displayed in many campaign appearances, that he would be president for all Americans.