About 10 loud explosions rocked the city around 1:30 am (1130 GMT), an AFP journalist said.
Shortly afterwards, Libyan television said "civilian and military sites" at the southeastern suburb of Khellat al-Ferjan had been targeted by "the colonialist aggressor."
Deputy Foreign Minister Khaled Kaaim meanwhile said late Thursday that rebel forces had sabotaged a pipeline in the Jebel Nefussa region, a mountainous area southeast of Tripoli.
"The rebels turned off a valve and poured cement over it," he said, adding that this would lead to a shortage of electricity in the capital as oil and gas were used at the Zawiyah refinery to generate power.
Kaaim said food and medicine supplies were spoiling in the capital due to long power cuts. Tripoli residents complained Thursday of extensive blackouts and an acute shortage of gas canisters.
NATO "wants to create a humanitarian crisis in Libya while the aim of its mission is to protect civilians," Kaaim said.
The Khadafi regime meanwhile tried to split the fractious Libyan opposition by claiming an alliance with Islamists.
|Libyan children stand amid the rubble outside a heavily damaged school in the coastal town of Zliten, 150 kilometres (95 miles) east of Tripoli, which a government official said was destroyed on August 4, 2011 in a NATO air strike earlier in the day|
After months of branding the entire opposition as radical extremists, the veteran leader's son Seif al-Islam of a pact with Ali Sallabi, a leading Islamic cleric in the rebel-held east.
Sallabi told AFP no pact existed, but he acknowledged that talks had taken place with Seif al-Islam.
"Our dialogue with them is always based on three points: Kadhafi and his sons must leave Libya, the capital (Tripoli) must be protected from destruction and the blood of Libyans must be spared. There is no doubt about these constants," he said.
The rebel-held east was in the grips of a fallout from the assassination of General Abdel Fatah Yunis.
A group of 28 tribes and civil actors met the insurgent government, pressing for a full and transparent investigation into Yunis's death.
The facts surrounding the general's death have been opaque, with senior members of the NTC giving incomplete and contradictory accounts of how he died, who killed him and the motive for the murder.
The rebels scored a minor victory Thursday, when a massive oil tanker steamed into the port of Benghazi.
The 182-metre (600-foot) long "Cartagena" docked shortly before midday local time (1000 GMT), the lip of its black hull pressed toward the water line.
A rebel soldier coming ashore said the vessel -- which was emblazoned with the initials of the state-owned General National Maritime Transport Company -- had been intercepted with the help of NATO two days ago "quite close to Tripoli."
"We had information about this boat with the help of NATO," said the rebel, who asked not to be named.
The fate of the crew was unclear, although the rebels said there was no resistance.
A NATO officer at the alliance's operational hub in Naples, Italy, said they had contact with the boat when it was hailed late on Wednesday afternoon.
Around 100 refugees fleeing Libya died on an overcrowded boat that arrived Thursday on the Italian island of Lampedusa, a survivor told the ANSA news agency after being rescued.
"We were 300, but around 100, especially women, did not survive, and the men were forced to throw their bodies into the sea," the female survivor was quoted as saying.