The United States said yesterday it had captured a suspected ringleader of the 2012 attack on the US diplomatic compound in Benghazi, Libya, a raid that killed four Americans including US ambassador to Libya Christopher Stevens, and ignited a political firestorm in Washington.

Rear Admiral John Kirby, the Pentagon press secretary, said US military troops, working with law enforcement personnel, captured Ahmed Abu Khatallah on Sunday in Libya and were holding him at a secure location outside the country.

A US official, speaking on condition of anonymity, said Khatallah was being held aboard an American ship after he was grabbed on the outskirts of Benghazi in an operation carried out by US special operations forces.

Kirby said there were no civilian casualties in the operation and all US personnel involved in the capture had safely left Libya. The Pentagon declined to discuss further details of the operation and it was not immediately clear whether there were non-civilian casualties.

A US official said Khatallah would be charged and prosecuted through the US court system and would not be sent to the prison for suspected al-Qaeda militants in Guantanamo, Cuba.

After the 2012 attack, which killed Stevens, Republicans accused the Obama administration of playing down the role of al-Qaeda in the attack for political reasons.

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