“We can confirm that the US government personnel supported a Ugandan operation successfully that apprehended several individuals suspected of being involved in the assassination of the principal state attorney,” Harf said on Wednesday.
“We can confirm that one of those detained in the operation was a former Guantanamo detainee who was released in 2006,” she added.
Harf stressed that the support was provided at request of Ugandan authorities.
Jamal Kiyemba is suspected of playing a role in the murder of Prosecutor Joan Kagezi, who was shot dead on March, 30 by gunmen on a motorcycle.
In 2002, Kiyemba was arrested in Pakistan on suspicion of having links to al-Qaeda, and was later transferred to the Guantanamo Bay prison facility in Cuba. Kiyemba was freed in 2006.
Attorney Kagezi handled international crimes and terror cases, and was the Assistant Director of Public Prosecution and Head of the International Criminal Division in Uganda's Ministry of Justice.