Libya is set to export more than two million barrels of crude oil this week from two ports in the east where output has topped 245,000 barrels per day, oil officials said.

Rising exports from the ports of Hariga and Zueitina offer some hope for the Opec member state's oil sector, which has been battered by Islamist militant attacks and fighting between rival factions.

Output from four fields including Sarir, the country's largest, has reached 243,000 to 245,000 bpd, said Omran al-Zwai, spokesman for state firm Arabian Gulf Oil Company (Agoco) which dominates production in eastern Libya.

Agoco restarted output at the Sarir and Messla oilfields after a pipeline blast cut off supplies to Hariga last month.

The two fields pump around 180,000 bpd, while Agoco also runs the Hamada and Nafoura fields. A fifth field, Bayda, has been closed to an outage, Zwai said.

A tanker has loaded 600,000 barrels of crude at Hariga while a second one will load one million this week, Zwai said.

The smaller port of Zueitina is expecting a tanker to load 630,000 barrels of crude later on Monday, an oil official said.

The tanker mark only the second time oil has been loaded at the port since April 2014 when a group campaigning for eastern autonomy ended a blockage. Strikes and technical delays have hampered efforts to export since.

The Zueitina official gave no output figure but an industry source put production last month at Harouge Oil Co and a field called 103 connected to Zueitina at around 30,000 bpd.

Libya also exports some 80,000 bpd from two offshore fields, while the eastern Brega port supplies Libya's Zawiya refinery.

This puts national output at about 400,000 bpd a day, still a fraction of the up to 1.6 million bpd Libya pumped prior to the 2011 uprising which toppled leader Muammar Gaddafi.

Major oilfields have stopped working due to the struggle between the recognised government in the east and a rival administration that took control of the capital Tripoli in August 2014.