Opposition fighters in Libya have been fending off fierce attacks by forces loyal to Muammar Gaddafi, amid reports of a rising death toll.
Gaddafi supporters moved eastward on Tuesday in an effort to push the rebels back and recapture fallen towns, with reports emerging that they have taken the central Libyan town of Bin Jawad.
The loyalists have moved on to the oil port of Ras Lanuf, which they had been bombarding with air raids.
Several people were reported to have been killed in battles a day earlier, including a family trying to flee the fighting.
There has also been fierce fighting in the eastern city of Misurata, located between the capital, Tripoli, and Gaddafi's hometown Sirte, with reports of at least 18 people killed.
On Sunday, rebels were filmed celebrating their victory over Gaddafi's forces there, but it was short-lived as fighting ensued on Monday, with rebels saying they feared Gaddafi forces were regrouping for further attacks.
Valerie Amos, UN under-secretary-general for humanitarian affairs and emergency relief co-ordinator, said in a statement that the Benghazi Red Crescent reported that Misurata was under attack by government forces again.
"Humanitarian organisations need urgent access now,'' she said. "People are injured and dying and need help immediately."
Witnesses also told Al Jazeera that Az-Zawiyah, west of Tripoli, was under heavy attack by government forces.
Meanwhile, Libyan state television has denied reports that Gaddafi tried to strike a deal with the rebels that would have seen him step down.
Gaddafi reportedly sent a representative to make a proposal to the opposition's so-called "National Council" based in Benghazi. It is said he wanted guarantees for his and his family's safety and immunity from prosecution.
A rebel spokesman confirmed that they received contact from the Gaddafi representative seeking to negotiate Gaddafi's exit.
"We rejected this. We are not negotiating with someone who spilled Libyan blood and continues to do so. Why would we trust the guy today?" Mustafa Gheriani, a media officer for the council told the Reuters news agency.
The report came as Al Jazeera's Jacky Rowland, reporting from the oil town of Brega, said government forces appeared to have "drawn a line in the sand" on the road to Sirte.
"If the rebels want to capture Sirte, they will have to prepare for heavy fighting along the way," she said.
At the hospital in Brega, 42 injured members of the opposition force were being treated, while at least eight were confirmed dead, our correspondent reported.
Jacky Rowland reports on the fight for Ras Lanuf
"The vast majority of those injured had been injured by their own weapons," she said, explaining that the rebels had little or no military training.
"People with no prior military experience, telling the soldiers that they want to fight and they want to fight in the anti-Gaddafi forces."
The government on Monday appeared to have solidified its control of Az-Zawiyah. The city had been the closest to Tripoli in opposition hands.
An Az-Zawiyah resident told the Associated Press news agency that government tanks and artillery opened fire on rebels around 9am local time and the attack had not stopped when he left the city at 1:30pm.
All entrances to the city were under government control and the rebels had been driven out of the city's central Martyr's Square and a nearby mosque by the heaviest attack in several days.
"The tanks are everywhere,'' he said. "The hospital is running out of supplies. There are injured everywhere who can't find a place to go."
For now, the Gaddafi government has managed to halt the rebel advance that began last week when fighters ventured beyond the opposition-controlled eastern half of the country.
Rebels plead for help
The rebel forces say they will be outgunned if the government continues to unleash its air attacks on them and are pleading for the international community to impose a no-fly zone to prevent this.
"We don't want a foreign military intervention, but we do want a no-fly zone," rebel fighter Ali Suleiman told AP.
"We are all waiting for one,'' he said. The rebels can take on "the rockets and the tanks, but not Gaddafi's air force''.
The US president said on Monday that the US and its NATO allies were still considering a military response to the violence even as Britain and France were drafting a UN resolution that would establish a no-fly zone.
Barack Obama said the US will stand with the Libyan people as they face "unacceptable'' violence. He also sent a strong message to Gaddafi, saying he and his supporters will be held responsible for the violence there.
William Hague, the UK foreign minister, said Britain is "working closely with partners on a contingency basis on elements of a resolution on a no-fly zone".
However, a British diplomat at the UN clarified that the draft resolution is being prepared in case it is needed but no decision has been made to introduce it at the Security Council.
The six US-allied Gulf Arab nations on Monday said they back a UN-enforced no-fly zone over Libya to protect civilians. The Gulf states also condemned the killings by pro-government forces in Libya as "massacres".
Abdul Rahman Hamad al-Attiyah, the secretary general of the Gulf Co-operation Council (GCC), said "the massacres committed by the regime" in Libya against its own citizens amount to "crimes against humanity".
The protection of Libyan citizens is an "absolute priority," al-Attiyah said. He was speaking late Monday at a meeting of the oil-rich group in the UAE capital Abu Dhabi.
Hundreds if not thousands of people have died since Libya's uprising began on February 14 in an effort to end Gaddafi's more than 41-year rule, although tight restrictions on media make it near impossible to get an accurate number.
More than 200,000 people have fled the country, most of them foreign workers. The exodus is creating a humanitarian crisis across the border with Tunisia.