A Palestinian student activist, who was detained by US immigration officers earlier this month, has spoken out for the first time about his arrest.

In a letter dictated over the phone to his family from an ICE detention facility in Louisiana, Mahmoud Khalil said he is a "political prisoner" and that he believes he was targeted for "exercising my right to free speech".

Born in Syria, Mr Khalil is a green card holder and recent graduate of Columbia University. He was a prominent figure during the Gaza war protests on campus in the spring of 2024.

His arrest has been linked to President Donald Trump's promise to crack down on student demonstrators he accuses of "un-American activity."

Trump has alleged repeatedly that pro-Palestinian activists, including Mr Khalil, support Hamas, group designated as a foreign terrorist organisation by the US. The president argues these protesters should be deported and called Mr Khalil's arrest "the first of many to come".

The day after, Mr Khalil's arrest, Secretary of State Marco Rubio reaffirmed the administration's stance, posting on X: "We will be revoking the visas and/or green cards of Hamas supporters in America so they can be deported."

The 30-year-old's lawyers have argued that he was exercising free speech rights to demonstrate in support of Palestinians in Gaza and against US support for Israel. They accused the government of "open repression of student activism and political speech".

In his letter, released Tuesday, Mr Khalil said he believes he was arrested because he "advocated for a free Palestine".

He also detailed his arrest, saying he and his wife were "accosted" on their way home from dinner by Department of Homeland Security agents "who refused to provide a warrant".

"Before I knew what was happening, agents handcuffed me and forced me into an unmarked car," he said, adding that he was not told anything for hours, including the cause for his arrest.

Mr Khalil said he spent the night at 26 Federal Plaza, a federal office building in New York that includes an immigration court. Later, he was transported to a detention facility in Elizabeth, New Jersey, where he said he was refused a blanket and forced to sleep on the ground.

He was transferred again to a detention facility in Louisiana, where he remains in custody. Mr Khalil's lawyers have been in court since to fight for his release.

Last week, his lawyers pushed to bring him back to New York and accused the Trump administration of attempting to restrict access to their client. The judge did not issue a ruling at the hearing, but directed prosecutors to prove why the case should take place elsewhere.

In his letter, Mr Khalil called his detention "unjust" and said it was "indicative of the anti-Palestinian racism that both the Biden and Trump administrations have demonstrated over the past 16 months."

He added that both administrations have "continued to supply Israel with weapons to kill Palestinians and prevented international intervention". He noted Israel's resumption of air strikes on Gaza on Monday night that killed 400, according to the Hamas-run health authority.

Mr Khalil also took aim at Columbia University's leadership for its disciplining of pro-Palestinian students, saying that the school's actions laid the groundwork for students like him to be targeted.

Columbia University has stated that law enforcement can enter campus property with a warrant, but the school denied that university leadership had invited ICE agents.

Amid the protests early last year, Mr Khalil was briefly suspended from the university, after police swarmed the campus following the occupation of a building.

At the time, he told the BBC that while he was acting as a key protest negotiator with Columbia officials, he had not participated directly in the student encampment because he was worried it could affect his student visa.

Back then, he said that he would continue protesting. But more recently, Mr Khalil's wife said her husband had grown worried about deportation, after facing online attacks that "were simply not based in reality".

She said he sent Columbia University an email asking for urgent legal help on 7 March, the day before immigration agents arrested him. Mr Khalil's wife, who is a US citizen, is now eight months pregnant.

The White House has continued to defend its move.

"This administration is not going to tolerate individuals having the privilege of studying in our country and then siding with pro-terrorist organisations that have killed Americans," said Karoline Leavitt, Trump's press secretary.

Mr Khalil said his story is a warning to others in the US, saying it is part of a broader strategy by the Trump administration to "suppress dissent."

"Visa-holders, green-card carriers, and citizens alike will all be targeted for their political beliefs," he warned.