Production has been suspended at Libyas Sarir oil field due to protests over wages at the eastern oil terminal of Hariga.
The oil field has the capacity to produce 100,000 barrels a day (b/d) of crude which is piped to Hariga for export.
Reuters quoted Omran al-Zwai, spokesman for Libyas eastern state oil firm AGOCO, saying that production at the Messla field would also be reduced to a minimum within four or five days if exports continue to be blocked.
The protests add to a raft of issues including conflict and political disagreements that have seen Libyan oil production drop since the government was overthrown five years ago.
Libya produced an average of 316,000 b/d in the second quarter of 2016 compared with 405,000 b/d over 2015. Production has fallen from a high of 1.6 million b/d in 2011.
Earlier this month, Libyas National Oil Corporation (NOC) agreed to merge with a rival energy company operating in the east of the war-torn African country, which was established by one of the countrys two former competing government.