Explosions shook Benghazi
while a fighter jet was heard flying overhead, and residents said the eastern rebel stronghold was under attack from Gaddafi's forces.
"The explosions started about 2 a.m. Gaddafi's forces are advancing, we hear they're 20 kms (12 miles) from Benghazi," Faraj Ali, a resident, said.
"It's land-based fire. We saw one aircraft," he added.
had declared a unilateral ceasefire on Friday after the United Nations Security Council authorised a no-fly zone over Libya, but the United States said the ceasefire was not being respected.
Libyan rebels said on Saturday they were being forced to retreat by Gaddafi's forces.
"They were 60 km (40 miles) away yesterday, today they are 20 kms away and they can be here in a half hour to 90 minutes," rebel fighter Khalid Ahmed told Reuters at a rebel base on the western edge of the city.
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.
LANDING BY BOAT
Jamal bin Nour, a member of a neighbourhood 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 rumours and hearsay that it is virtually impossible to verify due to lack of communications.
A unilateral ceasefire declared on Friday by the Libyan government appeared to have done little to convince outside powers to hold off on plans for air strikes to force an end to an increasingly bloody civil war.
Residents in the rebel-held western city of Misrata said they faced heavy bombardment on Friday -- a charge the government denied -- while a U.S. official said Gaddafi's forces were still advancing towards the rebels' eastern stronghold Benghazi.
Within hours of President Barack Obama saying the terms of a U.N. resolution meant to end fighting in Libya were non-negotiable, his U.N. envoy, Susan Rice, asked by CNN whether Gaddafi was in violation of these terms, said: "Yes, he is." Gaddafi said there was no justification for the U.N
"This is blatant colonialism. It does not have any justification. This will have serious consequences on the Mediterranean and on Europe," he said in comments reported by Al Jazeera television.
France, which along with Britain has been leading a drive for military intervention, will host a meeting on Saturday on Libya which will be attended by U.S. Secretary of State Hillary Clinton and Arab leaders.
"So I guess that after this summit, I think that in the coming hours, I think we will go to launch the military intervention," the French ambassador to the United Nations ambassador Gerard Araud told BBC's Newsnight.
Obama made clear any military action would aim to change conditions across Libya -- rather than just in the rebel-held east -- by calling on Gaddafi's forces to pull back from the western cities of Zawiyah and Misrata as well as from the east.
"All attacks against civilians must stop," Obama said, a day after the U.N. Security Council passed a resolution authorising international military intervention.
"Gaddafi must stop his troops from advancing on Benghazi, pull them back from Ajdabiya, Misrata and Zawiyah, and establish water, electricity and gas supplies to all areas. Humanitarian assistance must be allowed to reach the people of Libya.
"Let me be clear, these terms are not negotiable... If Gaddafi does not comply ... the resolution will be enforced through military action."
MISRATA BOMBED, RESIDENTS SAY
A U.S. national security official, who spoke on condition of anonymity, later said the troop movements by Gaddafi's forces towards Benghazi were "purposeful". The assessment was based on official reporting reaching U.S. national security agencies.
It was impossible to contact anyone on the frontline far to the west of Benghazi to find out what was happening. But in Benghazi, rebels dismissed the ceasefire declaration as a ruse.
"He is lying. His troops are advancing. We don't believe what Gaddafi says," said Mohammed Ishmael al-Tajouri, from the rebel coalition in Benghazi. "When he comes to Benghazi he will be fighting. There is no negotiating with Gaddafi." In Misrata, which like Zawiyah has been left stranded in the west while rebels who had advanced towards them from the east were beaten back by a counter-offensive by Gaddafi forces, residents said they had faced heavy bombardment on Friday.
One doctor said at least 38 people had been killed in the assault launched on Friday morning.
"Gaddafi's forces are bombarding the city with artillery shells and tanks," Dr Khaled Abou Selha told Reuters by satellite phone.
"They are even bombarding ambulances. I saw one little girl with half of her head blown off," he said, crying.
Another doctor, who declined to give his name, said by telephone late on Friday evening, "Now they are on the outskirts of the city. I can still hear bombing from time to time." In Tripoli the government said there had been no bombing since it announced the ceasefire.
"We have had no bombardment of any kind since the ceasefire was declared," Deputy Foreign Minister Khaled Kaim told journalists when asked about reports of continued government operations in Misrata and other parts of the country.
Kaim said Libya was asking China, Germany, Malta and Turkey to send observers to monitor its adherence to the ceasefire.
French Foreign Minister Alain Juppe said on Friday everything was ready to launch military strikes in Libya.
The United States, after embarking on wars in Afghanistan and Iraq, had insisted it would participate in rather than lead any military action. Obama said the United States would not deploy ground troops in Libya.