This artist's rendering shows US Magistrate, Judge John Facciola, swearing in the defendant, Libyan militant Ahmed Abu Khatallah, wearing a headphone, as his attorney Michelle Peterson watches during a hearing in Washington. Picture: Dana Verkouteren

Washington - A federal judge on Wednesday directed a Libyan militant charged in the 2012 Benghazi attacks that killed four Americans to remain in US custody after his own lawyer conceded that he had no reasonable chance of being released.

A lawyer for Ahmed Abu Khattala acknowledged that it was appropriate for her client to remain behind bars at the moment, given the nature of the charge he faces and his lack of ties to the United States. But she said she had so far seen no evidence of any role by Khattala in the September 11, 2012 attacks that killed the US ambassador to Libya, Christopher Stevens.

“What's been filed has shown, quite frankly, an utter lack of evidence of Mr. Khattala's involvement in the incident in Benghazi,” said Michelle Peterson, an assistant federal public defender, adding, “We are left to glean from press reports what the government's evidence is.”

Khattala's expected trial will take place alongside ongoing congressional and Justice Department investigations into the 2012 attack that killed an ambassador and the Obama administration's response to it shortly before the 2012 presidential election.

Prosecutors provided some new details in a court filing Tuesday night, arguing that he was part of a group of roughly 20 militants who stormed the diplomatic compound on the night of the attacks. They say he was motivated to participate in the attacks by an extremist ideology.

Abu Khattala appeared briefly in federal court in Washington, wearing a green prison jumpsuit and a long, graying beard. He listened to the proceedings through headphones as an interpreter translated the conversation into Arabic. Peterson requested that he be served a halal diet and be provided with a copy of the Quran.

Abu Khattala was captured in Libya more than two weeks ago and then brought to the United States aboard a Navy ship, where he was interrogated by federal agents. He has pleaded not guilty to a charge of conspiring to provide support to terrorists - a crime punishable by up to life in prison - but the Justice Department has said it expects additional charges soon.

The rampage in Benghazi on the 11th anniversary of the September 11, 2001 attacks has long been politically divisive. Republicans have criticized the response by Hillary Rodham Clinton, then the secretary of state, to the attacks. Republicans have accused the White House of misleading Americans and downplaying down a terrorist attack ahead of Barack Obama's re-election. The White House has accused Republicans of seeking political gains from the violence.