Libyan tribesmen staged a protest on Saturday at the giant El Sharara oilfield aiming to shut down the facility, engineers and a tribal spokesman said on Saturday, although it was not immediately clear if output had been halted.
A field engineer said crude was still flowing, while two other engineers said the field was apparently being shut down.
A spokesman for the tribesmen, who were protesting to demand more development for their communities, said they had closed the field located in south Libya.
"El Sharara is closed. We had given authorities a deadline but we got no response," said Mohammad Maighal, spokesman for the group that calls itself the Fezzan Anger Movement.
Fezzan is the historic name of the southern region to which the ElSharara oilfield belongs.
The field, which usually pumps about 300,000 barrels per day, has been repeatedly threatened by tribesmen asking for better health and other state services for poor, desert region.
Closing down an oilfield takes time so there was no final confirmation whether the wells had been turned off.
The state oil firm NOC usually tries to avert such action through talks.
NOC was not immediately available to comment.