Islamist militias in Libya have lost two major areas in the eastern city of Benghazi, military sources and residents have told the BBC.
“People are celebrating on the streets,” a resident said.
Fighters loyal to anti-Islamist Gen Khalifa Haftar are reported to have taken over the port, a hospital and have cut off a key weapons supply line.
Thousands have fled more than a year of fighting in Benghazi, the birthplace of the 2011 uprising.
Once in the Libyan army, Gen Haftar fought with revolutionaries to overthrow long-time leader Muammar Gaddafi.
Libya has since fragmented and has rival parliaments backed by various militias and brigades spawned by the uprising.
BBC North Africa correspondent Rana Jawad says the chaos has allowed Islamic State fighters to gain a foothold in the country, and some are believed to be fighting with other Islamist militias in Benghazi.
In January, the UN brokered a deal between rival lawmakers to form a unity government, but this has not yet happened.
The latest military gains will give Gen Haftar a stronger hand in Libya’s volatile political landscape, and it is not yet clear if he is giving his backing to the unity agreement, our correspondent says.
Last year, he was appointed as the head of armed forces for the parliament based in the eastern port city of Tobruk.
Some of the Islamist militias he has been battling in his hometown of Benghazi are backed by political factions in the west, where the Tripoli administration is based.
Who is General Khalifa Haftar?
- Helped Col Muammar Gaddafi overthrow Libya’s King Idris in 1969
- Libyan chief of staff until 1987, when he was disowned by Gaddafi after being captured in war with Chad
- Moved to the US state of Virginia after his release in the early 1990s
- Said to have had close ties with the CIA
- Devoted the next two decades to toppling Gaddafi
- Returned to Libya during the 2011 uprising against Gaddafi and became one of the main rebel commanders in the east
- Called on Libyans to rise up against the elected parliament in 2014
- Last year appointed head of the armed forces for the Tobruk parliament
Profile: General Khalifa Haftar