US Secretary of State Marco Rubio said the US has revoked at least 300 foreign students' visas as part of President Donald Trump's effort to clamp down on pro-Palestinian protesters on university campuses.

"Maybe more than 300 at this point," he said while speaking to reporters on a visit to Guyana. "We do it every day, every time I find one of these lunatics."

Rubio was asked to confirm how many student visas the administration had revoked in its crackdown on rhetoric at universities that it considers anti-Israeli.

The remarks follow immigration officials detention of a doctoral Turkish student attending Tufts University - an arrest the secretary defended.

A video of the student, Rumeysa Ozturk, being taken away by masked, plain-clothes officers to an unmarked car outside Boston, Massachusetts, has gone viral and sparked protests online.

Ms Ozturk is a Fullbright Scholar on an F-1 student visa and is in a doctoral program for Child Study and Human Development at Tufts.

Rubio was asked on Thursday why the Turkish student's visa was revoked.

"Here's why: I've said it everywhere, and I'll say it again," Rubio said. "If you apply for a student visa to come to the United States and you say you're coming not just to study, but to participate in movements that vandalize universities, harass students, take over buildings, and cause chaos, we're not giving you that visa."

It is currently unclear whether Ms Ozturk has been charged with anything.

Rubio did not provide any of the specific allegations against the 30-year-old, who has participated in pro-Palestinian protests. The Tufts student also co-wrote an opinion piece in the student newspaper last year that called for her university to divest from companies with ties to Israel and acknowledge "Palestinian genocide".

"Based on patterns we are seeing across the country, her exercising her free speech rights appears to have played a role in her detention," Mahsa Khanbabai, Ms Ozturk's lawyer, told Reuters.

This arrest is the latest in a string of actions taken against international students in the US who have expressed support for Palestinians.

Trump officials have said they are making use of the Immigration and Nationality Act, which allows the State Department to deport non-citizens who are "adversarial to the foreign policy and national security interests" of the US.

The arrests are a part of Trump's pledge to combat what the administration has classified as antisemitism, which was written into an executive order in January.

Since then, the White House has also revoked $400m (?308m) in Columbia funding over allegations the university failed to combat antisemitism on its campus, and threatened to do the same to other universities.

One of the highest profile arrests involves Columbia graduate Mahmoud Khalil, a prominent Palestinian activist, who remains in a Louisiana detention facility without charges.

Ms Ozturk was also taken to a detention centre in Louisiana. On Tuesday, a federal judge in Massachusetts ordered that Ms Ozturk be detained in Massachusetts, but federal records show she is still being held in Louisiana.

The government has been ordered to provide more information on Ms Ozturk's arrest by Friday.

US Homeland Security spokeswoman Tricia McLaughlin said earlier this week that Ms Ozturk "engaged in activities in support of Hamas, a foreign terrorist organization that relishes the killing of Americans".

Senator Elizabeth Warren, a Massachusetts Democrat, called the arrest "the latest in an alarming pattern to stifle civil liberties".

"The Trump administration is targeting students with legal status and ripping people out of their communities without due process. This is an attack on our Constitution and basic freedoms - and we will push back," she said in a statement.

On Wednesday, a federal judge ordered the Trump administration to halt its efforts to deport and arrest another student, Yunseo Chung of Columbia University. The 21-year-old is a legal permanent resident who moved to the US from South Korea as a child.

On Thursday, Rubio said the US gave students visa to earn a degree and "not become a social activist tearing up our campuses".

"If you lie, get the visa, and then engage in that kind of behaviour once you're here, we're going to revoke it," he said. (BBC, excluding headline)

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