Mahmoud Khalil, the Columbia University Palestinian graduate student who the Trump administration is seeking to deport for his role in pro-Palestinian protests, has called himself a political prisoner, in his first direct comments since his detention.

“My name is Mahmoud Khalil and I am a political prisoner,” Khalil said in a letter made public on Tuesday, according to Reuters.

“My arrest was a direct consequence of exercising my right to free speech as I advocated for a free Palestine and an end to the genocide in Gaza, which resumed in full force Monday night,” Khalil said in the letter, referring to the latest renewed Israeli strikes on Gaza that local authorities said killed over 400 Palestinians.

The detention of Khalil, a US permanent resident, has been condemned by multiple human rights groups as an assault on free speech and due process.

Over 100 Democratic lawmakers from the US House of Representatives have questioned the detention’s legality in a letter to the administration of Republican President Donald Trump.