Genera Haftar's forces took the Ras Lanuf and Al-Sidra terminals, together capable of handling 700,000 barrels of oil per day
A spokesman for forces led by a controversial Libyan general said on Sunday that they had seized two key oil export terminals in the country's east.
General Khalifa Haftar's forces took control of the Al-Sidra and Ras Lanuf ports, the LANA news agency loyal to Libya's internationally recognised parliament reported Colonel Ahmad Mesmari as saying.
Haftar, one of the most powerful military figures in Libya, has refused to endorse a UN-backed national unity government and remains loyal to the rival administration based in the east of the country.
Haftar's forces took the Ras Lanuf and Al-Sidra terminals, together capable of handling 700,000 barrels of oil per day, from installation guards loyal to the Tripoli-based Government of National Unity (GNA).
"Clashes are now ongoing near the Zuwaytina port" further east, Mesmari said.
The oil-rich area around Ras Lanuf and Al-Sidra is seen as a vital source of income for the GNA and key to the economy of the North African country.
In late July, the oil installation guards announced the reopening of Ras Lanuf and Al-Sidra ports after an agreement with the GNA to resume oil exports.
The ports had been closed for months following attacks by the jihadist Islamic State group in January.
IS has taken advantage of the turmoil in Libya since the 2011 uprising that toppled and killed longtime dictator Moamer Kadhafi, with rival authorities and militias vying for control of the country.
A UN-brokered deal in December led to the GNA starting to work in Tripoli, but it has since struggled to assert its authority over the country.