The security chief in the eastern Libyan city of Benghazi has been assassinated by gunmen, Belfast Telegraph reported.

Deputy interior minister Omar al-Khadrawi said National Security Chief Colonel Farag al-Dersi was shot dead while returning from work.

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

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 Gaddafi.

On September 11, American Ambassador Chris Stevens and three other Americans were killed in an assault on the US mission in Benghazi. Islamic extremists are believed to be behind the attack.