Explosions shook the Libyan city of Benghazi early on Saturday while a fighter jet was heard flying overhead, and residents said the eastern rebel stronghold was under attack from Muammar Gaddafi's forces.
"The explosions started about 2 a.m. Gaddafi's forces are advancing, we hear they're 20 kilometers (12 miles) from Benghazi," Faraj Ali, a resident, said.
"It's land-based fire. We saw one aircraft," he added.
Libya had declared a unilateral ceasefire on Friday after the United Nations Security Council authorized a no-fly zone over Libya, but the United States said the ceasefire was not being respected.
Elsewhere in the city, rebels also reported skirmishes and strikes by Gaddafi forces.
"Fighter jets bombed the road to the airport and there's been an air strike on the Abu Hadi district on the outskirts," Mohammed Dwo, a hospital worker and a rebel supporter, told Reuters.
He was speaking at the scene of an apparent firefight between rebels and what they claimed were two mercenaries who had infiltrated the city and were driving in a car which they said contained a crate of handgrenades.
The two men, in civilian clothes, had been shot and killed and rebels produced blood-soaked identity papers they said showed them to be of Nigerian nationality.
"We were sitting here and we received gunfire from this vehicle then we opened fire and after that it crashed," rebel fighter Meri Dersi said.
Jamal bin Nour, a member of a neighborhood watch group, told Reuters he had received a call to say government forces were landing by boat, but it was impossible to confirm the information.
The city has been so rife with rumors and hearsay that it is virtually impossible to verify due to lack of communications.
Gaddafi: UN resolution 'blatant colonialism'
The Libyan leader said there was no justification for a UN resolution aimed at ending violence in Libya and called it "blatant colonialism", al-Jazeera reported on Saturday.
Al-Jazeera said the remarks were made after Libya's response to the UN resolution were given by Foreign Minister Moussa Koussa on Friday but it was not immediately clear where he made the comments, which were aired by the television channel.
"This is blatant colonialism. It does not have any justification. This will have serious consequences on the Mediterranean and on Europe," he said.
"There must be safe air or sea navigation whatever the case. In 2011 they are colonising us, massacring us, and imposing one no-fly zone after the other and one military attack after an other. What is this racism? What is this hatred?"
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