Unidentified assailants gunned down a soldier outside his home and attacked a special forces base in Libya's second city Benghazi during the night, a security official said on Saturday.

There were no casualties in the attack on the base even though the assailants used rocket-propelled grenades, sub machineguns and an anti-tank mine, the official said, speaking on condition of anonymity.

Further east in the town of Derna, regarded as an Islamist stronghold, unidentified assailants blew up offices used by non-governmental organisations in a residential block, without causing any casualties.

The violence in Benghazi came after a policeman and a soldier were killed in the eastern city on Friday and four soldiers killed on Thursday amid mounting clashes between the army and well-armed jihadist group Ansar al-Sharia.