After riots and violent protests in and around their campus during the past three months, officials at the University of California at Berkeley said on Wednesday that the school is cancelling a planned speech by conservative firebrand Ann Coulter because of safety concerns.

In a letter to a campus Republican group that invited Coulter to speak, university officials said that they made the decision to cancel Coulter's appearance after assessing the violence that flared on campus in February, when the same college Republican group invited right-wing provocateur and Breitbart editor Milo Yiannopoulos to speak.

The violence and protests caused by Yiannopoulos's invitation garnered national attention and forced officials to put the campus on lock down. And after the university cancelled Yiannopoulos's talk, President Donald Trump criticised the school and threatened in a tweet to pull federal funds from UC-Berkeley.

The decisions by UC-Berkeley to cancel both events involving high-profile Republicans are especially notable given the campus's role during the 1960s and 1970s as the birthplace of the Free Speech Movement and its long tradition of social protest.

Coulter said in an email to The Washington Post on Wednesday that the university had been trying to force her to cancel her speech by “imposing ridiculous demands” on her but that she still agreed “to all of their silly requirements”. She said that she believes her speech “has been unconstitutionally banned” by the “public, taxpayer-supported UC-Berkeley”.

Controversial right-wing commentator Milo Yiannopoulos (Getty Images)

Coulter said the university insisted that her speech take place in the middle of the day, that only students could attend, and that the exact venue wouldn't be announced until the last minute. She said that she agreed with the conditions, but that apparently wasn't good enough.

“They just up and announced that I was prohibited from speaking anyway,” Coulter said, noting that her speech topic was to be immigration, the subject of one of her books. “I feel like the Constitution is important and that taxpayer-supported universities should not be using public funds to violate American citizens' constitutional rights.”

A conservative national group that was helping to organise the event, Young America's Foundation, said Coulter also made demands of her own, including that any students engaging in violence be expelled. In her email, Coulter said she is still planning to give her speech, and YAF spokesman Spencer Brown said she has told them she plans to appear at Berkeley on 27 April .

If Berkeley wants to have free speech, they are going to get it,“ Brown said.

A university spokesman said the school has not been in direct contact with Coulter but conveyed its concerns with the student group that invited her. He said the university was especially concerned that holding the event in the late afternoon would risk protests and potential violence stretching into the evening when the area would get crowded with commuters and students.

“Everything we're doing is so the speaker and students can actually exercise their rights without disruption,” Berkeley spokesman Dan Mogulof said. “It's unfortunate that there are people who think the university's efforts to keep students and the speaker herself safe are 'silly.'”

On Wednesday, university officials said they hope to reschedule Coulter's event for sometime in September, and they emphasised that they are not cancelling her event because of her controversial nature or sharply conservative views.

“It has nothing to do with anyone's political views. We believe in unqualified support to the First Amendment. But we also have an unqualified focus on safety of our students,” Mogulof said. “We are going to be making a concerted effort to explain the reasons behind this.”

On Saturday, protests again turned violent - though in the city of Berkeley, not the university campus - as pro-Trump and anti-Trump protesters clashed in the streets. The violence on Saturday was further heightened later in the day as far-left activists and far-right activists joined the fray.

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And on Tuesday at Auburn University in Alabama, three people were arrested amid protests and a fist fight that occurred over a speech by self-proclaimed white nationalist leader Richard Spencer.

At Berkeley, university officials said the recent violence has caused them to rethink where and when to hold such events. In their letter, university officials also partly blamed the college Republican group for inviting Coulter and setting a date for the event - 27 April - without consulting the university.

Officials learned of Coulter's event, the letter said, from reading about it in newspapers. And after consulting with university police, officials said, they could not find a venue available on that date that would allow them to protect Coulter, the audience and bystanders.