Witnesses in Libya say a series of explosions rocked the Tripoli area on Thursday shortly after NATO warplanes flew overhead.
Meanwhile, rebels have warned of what they call a "massacre" in the western city of Misrata unless NATO provides them more support against government forces.
A rebel spokesman said at least 23 people were killed in attacks by forces loyal to leader Moammar Gadhafi near Misrata Thursday.
In Washington, State Department acting spokesman Mark Toner said the U.S. remains confident in NATO's ability to oversee air operations in Libya. He commented after France asked for the United States to resume air raids.
France made the request on Thursday at a NATO meeting in Berlin. However, NATO chief Anders Fogh Rasmussen told alliance members that their forces have maintained a "high operational tempo" against legitimate targets in Libya. He also said NATO needs more high-precision attack aircraft for the mission.
Another conference about Libya was held in Cairo. U.N. Secretary-General Ban Ki-moon said the African and Arab and European delegates attending that meeting had agreed on a unified approach to finding a "lasting solution" to Libya's turmoil.
The talks in Berlin and Cairo took place a day after an international contact group of U.S., European and Arab partners pledged more monetary and political support for the Libyan opposition at a meeting in Doha. In its final statement, the group called on Mr. Gadhafi to leave power, saying he and his government had "lost all legitimacy."
In Brussels, the European Union announced Thursday that it has removed former Libyan Foreign Minister Moussa Koussa from a sanctions list, in an apparent bid to entice other Libyan officials to break ranks with the government. Koussa is the most senior official to flee Libya.
Some information for this report provided by AP, AFP and Reuters.