One of the men accused of planning the September 11, 2001 attacks was removed from a US military court on Tuesday after making an outburst about a secret CIA prison.

Yemeni defendant Ramzi Binalshibh, accused of helping the hijackers enter the United States and of financing the attacks that killed nearly 3,000 people, was ejected from a pre-trial hearing at the Guantanamo Bay prison camp on the judge's orders.

His removal came shortly after Binalshibh's lawyer suggested that guards at the US military prison in Cuba were deliberately depriving his client of sleep.

"He could not sleep at all last night because of the noise he is exposed to," said Navy Lieutenant Commander Kevin Bogucki. "He is too tired to pay attention."

The latest hearing for the alleged 9/11 plotters, who are eventually expected to go on trial in 2015, was screened for reporters at the Fort Meade military base in Maryland, via a closed-circuit feed.

Commander Bogucki said Binalshibh's cell was subjected to banging and knocking sounds -- an allegation the US government denies, but which the judge said had not been proven either way.

Having been granted a 15-minute recess to discuss whether Binalshibh understood his right to be present at Tuesday's hearing, the suspect refused to cooperate with Judge James Pohl's questions, citing bias.

"I refuse to answer this question as long as the judge is taking a position against me and against my allegations," Binalshibh said, before beginning apparently impromptu claims about US treatment of terror suspects.

After being warned by Judge Pohl that it was not his time to speak, the Yemeni suspect, whose alleged crimes include helping the hijackers find flight schools in the United States, cited the words "secret CIA prison" during a muffled speech.

Judge Pohl then told Binalshibh he would be removed if he did not stop talking, but the suspect continued and US military guards were instructed to take him to the court's holding cell.

The courtroom camera cut away from Binalshibh while he was being taken out of court.

All five suspects, including the self-proclaimed 9/11 mastermind Khaled Sheikh Mohammed, were present at Tuesday's hearing, all dressed in traditional white Arab robes and with several of them wearing desert-colored combat jackets.

The 9/11 tribunal is taking place against a background of a political push to shut down Guantanamo.

President Barack Obama pledged to close the site when he took office in January 2009 but has so far failed to do so, amid resistance in Congress to the idea of transferring detainees to US soil.

Following their detentions, in 2002 and 2003, the five 9/11 suspects spent three years in secret Central Intelligence Agency prisons abroad where they were subjected to harsh interrogation techniques, including the simulated drowning technique known as waterboarding, a practice that is widely considered torture.

Mohammed was waterboarded 183 times, according to US Justice Department memos.