Libya: Benghazi security boss latest killed in attack by suspected Islamic militant groups

Members of the Libyan extremist group Ansar al-Shariah seen at a protest in front of the Tibesti Hotel in Benghazi, Libya, Sept. 14, 2012.

TRIPOLI, Libya Libya's deputy interior minister says gunmen assassinated the security chief of the eastern city of Benghazi overnight.

Omar al-Khadrawi says National Security Chief Col. Farag al-Dersi was shot dead while returning from work on Wednesday.

"Three men opened fire, killed him and then fled the scene," he said, adding that it was unclear who is behind the killing.

On Sept. 11, U.S. Ambassador Chris Stevens and three other Americans were killed in an hours-long assault on the U.S. mission in Benghazi. Islamic extremists are believed to have been behind the attack.

The country's second largest city has witnessed a series of assassinations and car bombs over the past months by unidentified assailants targeting mainly security officials who worked under the rule of ousted dictator Muammar Qaddafi.