WASHINGTON - A federal grand jury issued a new indictment on Tuesday that includes a possible death penalty against Ahmed Abu Khatallah, a Libyan militant accused of involvement in the September 2012 attacks on the US diplomatic compound in Benghazi, Libya.

The indictment supersedes earlier accusations brought against Khatallah in July, and adds 17 charges, including allegations he led an extremist militia group and conspired with others to attack the facilities and kill US citizens.

Khatallah was captured in Libya in June by a US military and FBI team and transported to the United States aboard a US Navy ship to face charges in Washington federal court.

Khatallah's attorney, public defender Michelle Peterson, said she was not allowed to discuss any evidence the government had provided her in connection with the case, but she cautioned against a "rush to judgment."

"It's certainly not the first time the government has been wrong about Benghazi," she said.

Four Americans were killed in the attack, including the US ambassador to Libya, Christopher Stevens. The attack ignited a political firestorm in Washington that could still resonate if Hillary Clinton, secretary of state at the time of the attack, runs for president as expected in 2016.

Republicans accused Clinton of failing to put in place security measures to protect US personnel in Libya.

In the attack's immediate aftermath, Obama administration officials, including Susan Rice, currently White House national security adviser, stoked political controversy by initially saying the attack was a spontaneous protest against an anti-Muslim video that had surfaced in the United States.

Evidence later emerged that US agencies had been warning for months about weak security and possible attacks against US facilities in Libya. Evidence also emerged that soon after the attack, the United States had strong reason to believe that organized militant groups had been involved.

In media interviews before his capture by US forces, Khatallah denied involvement in the attacks against a compound used by the State Department as a consular office and a nearby compound used by the CIA as its Benghazi base.

The new US indictment alleges Khatallah had been the commander of an militant Islamist militia called Ubaydah bin Jarrah. That group later merged with another Libyan group called Ansar al Sharia, and Khatallah became one of its Benghazi-based leaders, US authorities said.