A security official says gunmen in an eastern Libyan city have killed a local politician who was a prominent opponent of Islamic militants controlling the city.

Rival radical groups have vied for control of Derna in Libya's oil-rich eastern region. Officials there say a number of hardened Libyan militants have recently patrolled the city flexing military power. Some have returned from fighting in Syria and Iraq.

The security official said Osama al-Mansouri was killed Tuesday when gunmen fired at his car. Al-Mansouri headed a political group that opposes Islamist groups and advocates autonomy for the east. The official spoke only on condition of anonymity because he wasn't authorized to speak to the media.

Assassinations have become a common way to settle political scores in increasingly lawless Libya.