NEW YORK (NYTIMES) - In New York, men shouted, "You're next!" at a black policewoman, making shooting motions with their hands.

In California, a high school student told a classmate, "You support Trump? You hate Mexicans!" before throwing her to the ground and hitting her.

Online, anonymous users tweeted, "Just reported you to ICE (Immigration and Customs Enforcement). Expect a van at your door tomorrow" to illegal immigrants.

Since voters elected Mr Donald Trump as president on Tuesday (Nov 8), outbursts of vitriol - verbal and physical - have been widely reported in the news and on social media.

Civil rights groups say their inboxes and call centres are lighting up with reports of attacks.

But the groups caution that it is too early to be certain how many of the accusations are legitimate, or how long the uptick will continue.

"It doesn't compare to the civil rights movement. No one is blowing up churches," said Mr Richard Cohen, president of the Southern Poverty Law Centre, which tracks hate groups. "But I don't think there's any question that there's been an increase."

While all sides of the political spectrum have reported problems, Mr Andrew Anglin, a vocal Trump supporter and a leader of the alt-right movement, called explicitly for intimidation of "brown people" on his neo-Nazi website, The Daily Stormer.

"I am of course against any violence against these people," he wrote. "However, I do think you should yell at them. We want them to feel that everything around them is against them. And we want them to be afraid."

The Southern Poverty Law Centre, created a webpage on Thursday (Nov 10) to funnel the reports, and received more than 200 within 24 hours. They also started an online petition, which had attracted more than 35,000 signatures as of Friday (Nov 11), asking Mr Trump to condemn the behaviour.

Many online attacks have stemmed from a small number of accounts, but have been shared widely, amplifying their affects, according to groups that monitor hate speech.

"The challenge is that these kinds of tweets generate millions and billions of media impressions," Mr Jonathan Greenblatt, chief executive of the Anti-Defamation League, said. "It allows these people to spread their venom with a velocity and a volume that was never before possible."

In addition to fear, celebration is among the most common causes of hateful outbursts, according to Dr Brian Levin, director of the Centre for the Study of Hate and Extremism at California State University, San Bernardino.

"When we have a catalytic event that is highly emotionally charged, we see an increase in hate crimes," Dr Levin said.

Analysing hate crime data to identify trends can take months, Dr Levin said. In the meantime, he said, it will be important to monitor non-violent activity like vandalism, verbal altercations and conflict on social media, which can escalate to violence.

While many of the widely shared complaints of harassment do not constitute criminal activity, they are stirring fear among marginalised groups.

Feeling helpless, Ms Iman Zawahry, who is Muslim, turned to Facebook to share with friends what her 12-year-old son had experienced in school in Gainesville, Florida.

The boy, whose United States-born parents are of Egyptian descent, had come home complaining that his seventh-grade classmates teased him about Mr Trump's victory and accused him of being part of Islamic State in Iraq and Syria (ISIS).

"He was very devastated - asking if he was going to be kicked out of the country," she said. "I'm feeling like a terrible mother. The more and more I push him for information, the more he gets upset. I'm in a complete panic."

Some abuse has been met with an outpouring of support. After black freshmen at the University of Pennsylvania received racist cellphone messages, including threats of lynching, en masse, classmates placed a huge safety pin in a campus quad to signify solidarity with them.

If Mr Trump were to publicly condemn acts of prejudice, experts say, it could have a neutralising effect because those who express hatred tend to respond to cues from role models.

Mr Trump signalled, in his victory speech on Wednesday (Nov 9), that his language may move in that direction, saying, "To all Republicans and Democrats and independents across this nation, I say it is time for us to come together as one united people."

Dr Levin, at the Centre for the Study of Hate and Extremism, said, "The more conciliatory he is, I think the better it will be because people look toward the media and role models as to how to frame their viewpoints."

At the same time, Dr Levin and his colleagues noted that no matter how Trump proceeds as president, the extremist groups that supported him, whose enthusiasm has been stoked by the election, are likely to react.

And because of that, those seeking to tamp down hate fuelled by race, religion or sexual orientation are "between a rock and a hard place."

"The rock is that these ideas will play a role in his administration," Dr Levin said. "The hard place is that when they don't, there will be a furious backlash because of the raised expectations."