Georgetown, Guyana - Secretary of State Marco Rubio said Thursday he has canceled the visas of more than 300 "lunatics" in a growing crackdown against Palestine solidarity activism on American university campuses.

Asked to confirm reports of 300 visas stripped, Rubio said: "Maybe more than 300 at this point. We do it every day."

"Every time I find one of these lunatics, I take away their visas," he told reporters on a visit to Guyana.

"At some point, I hope we run out because we've gotten rid of them," Rubio said.

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Since President Donald Trump returned to office on January 20, Rubio has moved aggressively against students at the forefront of on-campus protests calling on schools to divest from Israel amid the ongoing atrocities in Gaza.

The most high-profile case is Mahmoud Khalil, who led protests at Columbia University in New York. He was arrested this month and taken to Louisiana ahead of deportation proceedings, despite being a US permanent resident.

Rubio was asked about a new case at Tufts University in Massachusetts where immigration agents arrested a Turkish doctoral student, Rumeysa Ozturk, who had written an opinion piece in a campus newspaper demanding that the university recognize a genocide against the Palestinians – a claim supported by numerous human rights groups.

Congresswoman Ayanna Pressley, a Democrat from Massachusetts, accused the Trump administration of moving to "abduct students with legal status."

"This is a horrifying violation of Rumeysa's constitutional rights to due process and free speech. She must be immediately released," Pressley said in a statement.

The Trump administration has responded that the US constitutional protection of free speech does not apply to non-US citizens and claimed that activist students create a dangerous atmosphere for Jewish students.

Without commenting directly on the Tufts case, Rubio said: "If you tell us that the reason why you're coming to the United States is not just because you want to write op-eds, but because you want to participate in movements that are involved in doing things like vandalizing universities, harassing students, taking over buildings, creating a ruckus, we're not going to give you a visa."

"If you lie to us and get a visa and then enter the United States, and with that visa, participate in that sort of activity, we're going to take away your visa," he said.