A Libyan man identified as Ahmed Abu Khattala has been condemned to 22years imprisonment in Washington for his role in the 2012 Benghazi attack that murdered a United States ambassador and three others.

Prosecutors were unable to convince a jury that Khattala, leader of a militant group who had been photographed watching the attack on September 11, 2012, was directly to blame for the deaths of US Ambassador Christopher Stevens, a second State Department official, and two CIA contractor guards at the consulate and a CIA annex.

He was convicted of only four of 18 charges he faced: supporting terrorists, conspiracy to provide support to terrorists, carrying a semi-automatic weapon during a violent crime, and damaging US property.

That was far weaker than the picture prosecutors had presented of Khattala as the person who plotted and directed the deadly assault.