US Secretary of State Marco Rubio said that the US has canceled at least 300 visas of foreign students as part of President Donald Trump’s effort to stop pro-Palestinian protests on university campuses.

“Maybe more than 300 at this point,” he told reporters during a visit to Guyana. “We do it every day, every time I find one of these lunatics.”

Rubio was asked how many student visas had been revoked in the government’s crackdown on what it sees as anti-Israeli speech at universities.

His comments came after immigration officials arrested a Turkish doctoral student from Tufts University. Rubio defended the arrest.

A video of the student, Rumeysa Ozturk, being taken away by masked officers in plain clothes to an unmarked car in Boston, Massachusetts, has spread widely online and led to protests.

Ozturk is a Fulbright Scholar with an F-1 student visa and is pursuing a PhD in Child Study and Human Development at Tufts.

When asked why her visa was revoked, Rubio responded:

“Here’s why: I’ve said it everywhere, and I’ll say it again,” he 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 unclear if Ozturk has been charged with any crime.

Rubio did not mention any specific allegations against the 30-year-old, who has been involved in pro-Palestinian protests. Last year, she co-wrote an article in the university’s student newspaper urging Tufts to stop investing in companies linked to Israel and recognize what she called a “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,” her lawyer, Mahsa Khanbabai, told Reuters.

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

Officials from the Trump administration say they are using the Immigration and Nationality Act, which allows the State Department to deport non-citizens who are considered a threat to US foreign policy or national security.

These arrests are part of Trump’s promise to fight what his administration has labeled antisemitism, which was included in an executive order issued in January.

Since then, the White House has also cut $400 million (about £308 million) in funding for Columbia University, accusing it of failing to stop antisemitism on campus. Other universities have been warned that they could face similar cuts.

One of the most notable arrests is that of Columbia graduate Mahmoud Khalil, a well-known Palestinian activist who is being held in a Louisiana detention center without charges.

Ozturk has also been sent to a detention center in Louisiana. A federal judge in Massachusetts ordered on Tuesday that she should be held in Massachusetts, but government records show she is still in Louisiana.

The government has been told to provide more details about her arrest by Friday.

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

Senator Elizabeth Warren, a Democrat from Massachusetts, 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 stop 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 gives student visas for education, not activism.

“If you lie, get the visa, and then engage in that kind of behavior once you’re here, we’re going to revoke it,” he said.

With inputs from agencies