|Forces loyal to Gaddafi have thwarted opposition efforts to topple his government for the last five months [EPA]
NATO jets have struck a military storage facility and other targets in the eastern outskirts of the capital, Tripoli.
Sunday's attacks came two days after major international players recognised Libya's opposition leadership as the country's legitimate representative.
Opposition advances on the eastern oil city of Brega, meanwhile, stretched into their fourth day, with reports of pitched street battles in residential areas.
From Tripoli, bright flashes could be seen on the eastern horizon just after midnight, followed by a steady rumbling that went on for an hour.
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Fighter jets could be heard crisscrossing the night sky lit up by a near full moon, and were heard until Sunday afternoon.
NATO said its forces hit a military storage facility, along with three radar sites and an anti-aircraft missile launcher east of Tripoli.
The state television channel Al Jamahiriya reported that "the colonialist Crusader aggressor", a reference to NATO, had raided civilian and military sites in the Ain Zara district and Tajoura in the eastern suburbs of Tripoli.
The opposition has received a boost from its recognition by the Contact Group on Libya at a conference in Turkey on Friday and a pledge to transfer Libya's billions in frozen assets to its coffers.
Nevertheless, the struggle against Muammar Gaddafi has settled into a stalemate since the mass uprising against his rule broke out in mid-February.
The fighters have set up an interim administration in the eastern city of Benghazi and seized control of the port city of Misurata and much of the western Nafusa Mountains.
Gaddafi controls the rest of Libya from his stronghold in Tripoli.
Battle at Brega
NATO reported it flew a total of 110 sorties and carried out 45 attacks on Saturday.
Its forces also struck several targets around Brega, possibly in support of the opposition assault on the town, destroying a tank, a pair of rocket launchers and five vehicles.
Mohammed al-Rajaly, a spokesman for the Libyan opposition, said there is street-to-street fighting with automatic weapons in Brega, representing the farthest the fighters have reached in their months of trying to retake the town.
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Brega is the transport terminal for oil and natural gas pumped from the fields deep in Libya's south and has changed hands several times in the fighting.
One fighter was killed and 15 were wounded, according to Mohammed Idris, a doctor at the hospital in the nearby city of Ajdabiya.
On Saturday, 10 opposition fighters were killed in a failed assault.
On the whole, however, their efforts to move on Tripoli have got bogged down in the face of better-equipped and trained government troops.
"Each time the opposition fighters try to advance to an area where Gaddafi loyalists have been stationed, they hit a minefield," Al Jazeera's Hoda Hamid, reporting from the northern city of Misurata on Sunday, said.
"Now this is a problem for them ... and as they try to push further east or west, the problem will become bigger."
Gaddafi, vowing to remain in the land of his ancestors, has made a series of defiant speeches over the last few days, ridiculing NATO and making it clear he has no intention of leaving power - as demanded by Western powers.
Al Jamahiriya showed Gaddafi addressing over the phone a crowd in the northwestern town of Az Zawiyah on Saturday.
"I will die for my people, I will never leave my people. If you allow me to lead the fight, I will lead the fight and die for my country," he was heard saying.
"We need to go to Benghazi and Misurata to liberate it. The people are calling me, saying 'come and help us'. Families are telling us 'we are being used as human shields in Misurata, women are getting killed'.
"The Libyan people will die for its oil. We will not leave our oil for these gangs."
Gaddafi described the opposition as worthless traitors and rejected suggestions that he was about to leave the country.
"They said Gaddafi will go to Honolulu," he said. "This is funny: to leave the graves of my forefathers and my people? Are you serious?"
Source: Al Jazeera and agencies