Fighting raged across Libya after rebels denied they were in talks with Muammar Qaddafi's regime.
Sources close to the Tunisian security services on August 15 had reported such talks in Djerba, near the border with Libya, as rebel forces drew closer to Tripoli and claimed to have cut vital supply lines to the capital.
But UN spokesman Farhan Haq said the international body had "no concrete information" on any talks in Tunisia and that its Libya envoy, Abdul Ilah al-Khatib, was not taking part in any such talks.
In the west of the country, Qaddafi's forces shelled the centre of Zawiyah on August 15 hours after rebels claimed they had seized control of most of the strategic port.
Earlier, the rebels said they had also seized Gharyan, a town in the Nafusa Mountains that straddles the road connecting Tripoli with Sabha.
The United States expressed optimism that the rebels were closing in on Qaddafi, who has ruled for over 40 years, with White House spokesman Jay Carney saying the increasingly isolated strongman's "days are numbered."
U.S. officials also said Libyan government forces fired a Scud missile for the first time in their six-month-old conflict with rebels fighting to end Muammar Qaddafi's regime.
A U.S. defense official said the missile was fired early on August 14 from near the town of Sirte and landed in the desert outside the port city of Brega, injuring no one.
A rebel spokesman, Ahmed Bani, speaking to Reuters, said the Scud firing was yet further proof Qaddafi's regime had lost legitimacy.
"In fact the tyrant's regime possesses such missiles and they are able to use them. This man will use any weapon necessary to keep his regime going and resume his rule, even for a few hours," Bani said.
"We are used to facing such unpredictable and crude behavior from those who have lost legitimacy and credibility."
A NATO spokesman said the launch of the scud missile was a "desperate gesture" by the regime in the face of territorial gains by the opposition.
compiled from agency reports