The Libyan militia leader suspected in the 2012 attack on the US diplomatic mission in Benghazi that killed four Americans was in federal custody yesterday morning, the US attorney’s office in Washington said.

“Ahmed Abu Khatallah is in law enforcement custody,” said Bill Miller, spokesman for the US attorney’s office for the District of Columbia.

CNN and The New York Times reported that Khatallah was taken to a federal court in Washington from a Navy warship where he had been held since his June 15 capture.

Miller would not comment on where Khatallah was being held, but there was there was heightened security around the federal courthouse building near the US Capitol in Washington, with two or three US marshalls at each of the building’s corners.

Khatallah was taken aboard the USS New York, an amphibious transport ship, after his seizure by US special operations forces in a raid on the outskirts of Benghazi. He is expected to be prosecuted in the US criminal justice system.

US Ambassador Christopher Stevens and three other Americans died in the September 11, 2012, attack. Khatallah is charged with killing a person on US property, a firearms violation and providing material support to terrorism.

The charges were filed in July 2013 but kept under a court seal until this month.

Khatallah’s capture was a victory for US President Barack Obama, who has been accused by Republicans of playing down the role of al-Qaeda in the 2012 attacks for political reasons and being slow to deliver on promises of justice.

Republicans also said then-Secretary of State Hillary Clinton had failed to take steps to ensure the safety of American diplomatic personnel, an issue that is still resonating as Clinton considers running for US president in 2016.

Some Republican lawmakers had called for Khatallah to be taken to the US prison at Guantanamo Bay, Cuba, for military prosecution, but Obama’s policy has been to try terrorism suspects caught abroad in the US justice system.