Attempts to secure a truce in Libya have failed and the humanitarian crisis is worsening, UN chief Ban Ki-moon has told AFP, while NATO on Thursday said Moamer Kadhafi's military power has been significantly degraded.
Rebels fighting to overthrow the Libyan strongman said meanwhile they were increasingly concerned about the humanitarian situation in the Nafusa mountains even after a gaining control of the western lifeline city of Misrata.
UN secretary general Ban said his special envoy to Libya, Abdul-Ilah al-Khatib, has been "working very hard" without progress to report in his efforts to sway Kadhafi to declare an immediate and verifiable ceasefire.
"In view of the deteriorating humanitarian situation, the crisis is getting worse," he warned in an interview in New York.
Ban said he was very concerned about rebel-held Misrata, which was under siege from Kadhafi forces for more than two months and where hundreds were killed. "The situation is getting very bad," he said.
Khatib travelled to Tripoli on Sunday where he held talks with officials on the need for a ceasefire and access to stricken cities.
He did not meet Kadhafi, who has been stubbornly refusing to call a halt the conflict which erupted when he ordered his forces to put down pro-democracy protests launched on February 15 against his autocratic four-decade rule.
Thousands of people have died in clashes between rebels and loyalists, and some 750,000 have been forced to flee, according to the International Criminal Court and the United Nations.
Having lost vast swathes of Libya's east to rebels, and with almost daily bombardments by NATO jets acting under a UN mandate to enforce a no-fly zone and protect civilians, the regime has its back to the wall.
Rebels said Thursday they were increasingly concerned about a humanitarian crisis in the Nafusa mountains in the west, where Kadhafi forces were blocking humanitarian aid and the evacuation of the wounded.
"Our biggest concern is the western mountain range," rebel spokesman Jalal al-Gallal told AFP.
Gallal said the rebels were suffering "heavy losses" on the outskirts of the western city of Misrata, where they were being ambushed by Kadhafi loyalists despite having secured the airport on May 12.
Earlier, NATO chief Andres Fogh Rasmussen said Kadhafi's military power has been significantly degraded which would lead to the eventual collapse of his regime.
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"We have significantly degraded Kadhafi's war machine and now we see the results -- the opposition has gained ground," said Rasmussen, adding "the Kadhafi regime is more and more isolated every day."
"I'm confident that a combination of a strong military pressure and increased political pressure and support for the opposition will eventually lead to collapse of the regime."
Kadhafi's position has become more precarious after a call by International Criminal Court chief prosecutor Luis Moreno-Ocampo for arrest warrants against the strongman, his second-oldest son Seif al-Islam and his brother-in-law Abdullah al-Senussi -- for crimes against humanity.
Libya's government has dismissed the ICC's bid, saying the court has no jurisdiction over Tripoli while denying accusations the regime ordered the killing of civilians or hired mercenaries against them.
Authorities in Tunis on Thursday denied reports Kadhafi's wife and daughter had fled and arrived in Tunisia.
Elsewhere, Croatia's foreign ministry said Thursday it ordered Libya's charge d'affaires to leave the country, accusing him of inappropriate activities without elaborating.
And Norway's military said it had been the victim of a serious cyber attack at the end of March, a day after Norwegian F-16 fighter jets carried out bombings in Libya for the first time.
"The army is regularly the target of cyber and virus attacks, but not as extensive as this," Hilde Lindboe, a spokeswoman for Norwegian Defence Information Infrastructure, told AFP.
"From what we have seen, no sensitive information has been obtained," Lindboe said.
The increasingly confident rebels laid claim Wednesday to being able to represent Libya at the June 8 OPEC meeting in Vienna, amid reports Kadhafi's oil minister has defected.
Libya is a key crude exporter but its output has been slashed since the revolt erupted in mid-February.
Oil Minister Shukri Ghanem, who was due to attend the Vienna meeting, at the weekend crossed from Libya into neighbouring Tunisia, a Tunisian official said, although there has been no confirmation he has defected.