A car bomb killed a prominent tribal elder allied to eastern security forces and five other people outside a mosque in a town south of Benghazi as they were leaving afternoon prayers on Friday, a security official said.
There was no immediate claim of responsibility but rivals of the eastern-based Libyan National Army (LNA) have previously carried out similar attacks in Benghazi targeting figures associated with the LNA.
The blast in Suluq, 31 miles (50 km) south of Benghazi killed Ibrayk Al-Awati, an elder of the Al-Awaqir tribe, and 11 wounded 11 other people, the official said.
The LNA has been fighting a three-year campaign against Islamist militants and other opponents in Benghazi and other parts of eastern Libya.
Images shared on social media showed flames and plumes of black smoke rising from the shell of a car, with debris and blood on the ground nearby.
Libya has been split since 2014 between rival governments aligned with loose and shifting armed alliances based in the east and west of the country.