TRIPOLI, Libya  — Protesters have shut down the eastern Libyan oil port Brega, state firm National Oil Corp said on Saturday, days after the government celebrated the reopening of major ports following almost a year of blockage.

NOC spokesman Mohamed El Harari said the state-run Sirte Oil Co would have to shut down its production of 43,000 barrels per day if the protest by state oil guards continued, without being more specific about time frame.

Harari said he did not know what the demands of the guards were. He said Brega port was used to export oil but recently had been mostly used to supply the western Zawiya refinery.

Last week the government managed to negotiate an end to a protest blocking the 340,000 barrels per day El Sharara field in the southwest. A rebel group also agreed to restart the eastern Ras Lanuf and Es Sider ports which they had seized almost a year ago.

The protesters at Brega are members of the petroleum facilities guards (PFG), a force made up mainly of former militia fighters who helped oust Moammar Gadhafi in 2011.

The government in Tripoli has tried to co-opt the militias by integrating them into state forces like the oil guards but it has been unable to control them with its fledgling army, which is still in training.

Members of the PFG often seize oil facilities they are supposed to protect to press the central government into meeting political and financial demands, part of growing turmoil in the North African country.

Libya used to produce 1.4 million barrels per day until July 2012, when a wave of protests started. Its current output is 350,000 barrels per day, following the restart of the El Sharara field, NOC said on Thursday.

Disputes over Libya's oil resources have been among the many triggers for conflict between rival brigades of former rebels and allied political factions since civil war ended four decades of Gadhafi rule.