Explosions were heard in Tripoli on Monday night and into Tuesday morning -- the latest in several rounds of bombings in the last two days, a Reuters witness said.
Libyan TV said al-Karama neighbourhood was hit by NATO forces, which have been bombing targets of Gaddafi's government since March.
It later said a telecommunications station was hit in a bombing.
"The crusading colonial aggressor this evening hit and destroyed a communications centre west of Tripoli, severing land communications in some areas. The station is civilian," it said.
Rebels control the east of Libya, the western city of Misrata and the range of mountains near the border with Tunisia. But they have been unable to advance on the capital against Gaddafi's better-equipped forces, despite NATO air strikes.
Rebels seized Yafran, 100 km (60 miles) southwest of Tripoli, on Monday after British warplanes destroyed two tanks and two armoured personnel carriers on June 2.
Yafran is spread over a hill, the bottom part of which had been controlled by pro-Gaddafi forces for more than a month and used to besiege the rebel-controlled part.
Food, drinking water and medicines were running short.
Asked about reports of rebel gains in the Western Mountains area, Libyan Deputy Prime Minister Khaled Kaim told reporters government forces could retake rebel territory in hours, but were holding back from doing so to avoid civilian casualties.
NATO attack helicopters were in action in the east on Sunday. Apaches destroyed a rocket launcher system on the coast near the eastern town of Brega, Britain's Defence Ministry said.
A French military source said French planes and helicopters had been in Libya every night since Friday, but gave no details.
Gaddafi's forces also fired rockets into the rebel-held town of Ajdabiyah in the east on Monday and clashes broke out on the main road further west, rebel sources said.
Gaddafi's troops and the rebels have been in stalemate for weeks, with neither able to hold territory on a road between Ajdabiyah and the Gaddafi-held oil town of Brega further west.
The new deployment of the helicopters is part of a plan to step up military operations to break the deadlock. Critics say NATO has gone far beyond its U.N. mandate to protect civilians.
In a report on Monday, the International Crisis Group (ICG) urged the rebels and their NATO allies to propose a ceasefire.
"The (rebels) and their NATO supporters appear uninterested in resolving the conflict through negotiation," it said.
"To insist, as they have done, on Gaddafi's departure as a precondition...is to prolong the military conflict and deepen the crisis. Instead, the priority should be to secure an immediate ceasefire and negotiations on a transition."
Western governments and rebels say a combination of NATO air strikes, diplomatic isolation and grassroots opposition will eventually bring an end to Gaddafi's rule.
But Gaddafi says he has no intention of stepping down. He insists he is supported by all Libyans apart from a minority of "rats" and al Qaeda militants, and says the NATO intervention is designed to steal Libya's abundant oil.
In Brussels, NATO Secretary General Anders Fogh Rasmussen sidestepped questions on whether more helicopters were needed, but he said he would repeat calls for NATO allies to step up involvement during a NATO defence ministers meeting this week.
"In general terms, I will request broad support for our operation in Libya, if possible increased contributions, if possible more flexible use of the assets provided," he said.
NATO last week decided to extend operations in Libya for another 90 days, or until the end of September.
Spanish Foreign Minister Trinidad Jimenez will travel to the Libyan city of Benghazi to meet rebel leader Mustafa Abdel Jalil on Wednesday, her ministry said in a statement on Monday.
In Beijing, the Chinese Foreign Ministry said an Egypt-based Chinese diplomat also had visited Benghazi for talks with the rebel-led National Transitional Council, adding to signs that China is courting the insurgents.
The diplomat went to the city to "understand the local humanitarian situation and the state of Chinese-funded firms", the Foreign Ministry said in a statement on its website (www.mfa.gov.cn) late on Monday.
The diplomat met leaders of the rebel council, the statement said, without giving details.