A Libyan security official said gunmen have shot dead an officer in the air defense branch in the Eastern city of Benghazi. The official says Colonel Wanis Massoud al-Barghathi was gunned down Friday night. He didn't provide further details, and spoke on condition of anonymity because he was not authorized to brief the media, AP reported. A wave of assassinations and bombings has targeted police and army officers in Benghazi, a stronghold of militias with roots in the rebel brigades that fought against slain dictator Moammar Gaddafi. Some of the groups are hard-liners with Al-Qaeda links.