Libyan tribesmen staged a demonstration at the eastern oil port of Hariga on Thursday in protest against the appointment of a government minister, a leading member of the tribe said.
It was not clear whether oil exports from the port, located in Tobruk near the Egyptian border, had been affected.
A spokesman for port operator AGOCO, part of state oil firm NOC, declined to comment.
"We are at the port's gate. No car can enter or leave the port," a member of the powerful Obeidat tribe, told Reuters, asking not to be identified.
He said tribesmen were protesting a decision by the internationally recognized government in Tripoli to appoint Ali Essawi as economy minister.
Hariga lies in eastern Libya, run by a rival administration.
Libyan prosecutors had in 2011 named Essawi as the main suspect in the killing of Abdel Fattah Younes, a former top rebel commander during the uprising against Moammar Gadhafi in 2011. Younes belonged to the Obeidat tribe.
A Libyan court in 2012 had dropped the case against Essawi and other suspects. But he re-entered the spotlight when Tripoli-based Prime Minister Fayez al-Sarraj appointed him as economy minister this month.
Khalifa Haftar, a top commander whose troops control the east, this week ordered a new investigation into the killing of Younes. His killing had caused deep rifts in the rebel camp, which later took over the oil-producing country.
Younes was for years part of Gadhafi's inner circle. He defected at the start of the uprising in February 2011 and became the military chief of the rebellion, a move opposed by other rebels who had suffered under the old regime.
The circumstances of his killing remain murky, but it is known that he was slain in July 2011 after rebel leaders summoned him back from the front line to Benghazi, cradle of the uprising.