The gunmen were equipped with trucks carrying anti-aircraft weapons, The Guardian reported. They blocked traffic on Libya's major east-west highway at Red Wadi near the Ras Lanuf refinery.
Elections for representatives to the national congress, the new Libyan province, are scheduled for July 7. The militia said the rules should be changed to give Cyrenica, the eastern province known in Arabic as Barqa, more seats.
The Barqa Council has threatened a boycott of the elections unless the rules are changed. The province has the lion's share of Libya's oil.
Libya has been hit by violence and dissension since the fall of its longtime strongman, Moammar Gadhafi. In the south, fighting between the indigenous Tibu and Arabs, which has taken around 170 lives, has flared up again, while Islamists have staged attacks in Benghazi, the newspaper said, the eastern city that was the first center of the revolt against Gadhafi.