WASHINGTON -- The Libyan militant accused of masterminding the deadly Benghazi attacks that have become a flashpoint in U.S. politics pleaded not guilty to conspiracy Saturday in a federal courtroom in Washington.

Ahmed Abu Khattala made his initial court appearance amid tight security.

A says Abu Khattala took part in a conspiracy to provide material support and resources to terrorists in the 2012 attacks that killed U.S. Ambassador Chris Stevens and three other Americans.

In court, he wore a two-piece black track suit and kept his hands, which were not handcuffed, behind his back. He looked impassively at the judge for most of a 10-minute court hearing.

His court appointed lawyer, Michele Peterson, entered the not guilty plea.

U.S. Magistrate Judge John Facciola ordered the defendant's continued detention, but Facciola did not say where Abu Khattala would be held.

The indictment was handed up under seal on Thursday and was made public Saturday afternoon.

The government said it would file more charges against him soon.

Abu Khattala spoke just two words during the hearing, both in Arabic. He replied "yes" when asked to swear to tell the truth and "no" when asked if he was having trouble understanding the proceeding.

He wore headphones to listen to a translation of the proceedings. He had a beard and long curly hair, both mostly gray.

Associated Press writers Pete Yost and Robert Burns contributed to this report