Libya: Pro-Gaddafi forces attack rebel-held Ras Lanuf
Pro-Gaddafi forces have launched several air strikes on Libya's rebel-held oil port of Ras Lanuf.
One attack destroyed a car carrying a family, killing at least one person, Reuters agency reported.
Bin Jawad, 50km (30 miles) to the west, has fallen to forces loyal to Libyan leader Col Gaddafi, correspondents say, checking the rebels' westward progress.
The UN says 200,000 people have fled the violence, where the revolt is well into its third week.
Nato is considering military options in response to the situation in Libya, US President Barack Obama has said.
"We send a very clear message to the Libyan people that we will stand with them in the face of unwarranted violence and the continuing suppression of democratic ideals that we have seen there," he said.
Throughout Monday, rebels fought off an intense counter-offensive by Gaddafi forces, which have been attacking towns both near Tripoli and in the east after recent rebel gains.
The Gaddafi regime is in a belligerent, confident mood, says the BBC's Wyre Davies in Tripoli. But, he adds, it is increasingly difficult to know how much is fact and how much is propaganda, as the Libyan government is making it almost impossible for journalists to visit areas where many people are thought to have been killed in the fighting.
As well as the attacks on Ras Lanuf, 600km (400 miles) east of the capital, pro-Gaddafi forces launched a renewed tank and artillery attack on Zawiya, a rebel-held town 50km west of Tripoli, Reuters reported an exiled Libyan opposition group as saying.
In Misrata, 200km (125 miles) east of the capital, a local doctor told the BBC that 21 bodies and more than 100 wounded people had been brought to his hospital, which he said was also targeted by government troops.
He said the fighting went on for at least six hours, with residents saying the city centre was "seriously destroyed".
With a population of 300,000, Misrata is the largest town controlled by rebels outside their stronghold in the eastern part of the country.
Residents have called for the international community to establish a no-fly zone over Libya to prevent Col Gaddafi's air force from attacking.
The UK and France have drawn up elements of a UN resolution authorising such a no-fly zone, a British diplomat says.
This was contingency planning in case world leaders decided such a zone was necessary, the diplomat told the BBC: there were no current plans to table the resolution or launch negotiations.
Possible triggers for such a move might be a massive humanitarian emergency or gross and systematic violations of human rights, diplomats say.
Russian Foreign Minister Sergei Lavrov has reiterated his opposition to military intervention in Libya, the RIA Novosti news agency reports. Russia has the power to veto any UN Security Council resolution.
Events in Libya were "absolutely outrageous", Nato Secretary General Anders Fogh Rasmussen told the BBC, adding that "systematic attacks against the civilian population may, as stated by the UN Security Council, amount to a crime against humanity".
However, he said Nato had no plans to intervene, and any operational role would be pursuant to a UN mandate.
The Gulf Arab states have also condemned the use of violence by pro-Gaddafi forces, and demanded that the UN Security Council enforce a no-fly zone over Libya.
The UN's latest figures show at least 191,748 people have fled the violence in Libya since the fighting began, and that more want to leave but have not made it to a border or are constrained from crossing.
Meanwhile, Libyan Foreign Minister Mussa Kussa openly ridiculed the UK and other Western governments for trying to make contact with rebel leaders in the country's east.
Six soldiers and two Foreign Office officials were detained for two days by rebels in eastern Libya, but were freed on Sunday and left the country.
UK Foreign Secretary William Hague said the men were withdrawn after a "serious misunderstanding" over their role.
Mr Kussa said that by sending a special forces unit to escort a diplomat in rebel-held territory, the UK was part of "a conspiracy to divide Libya".
UN Secretary General Ban Ki-moon has appointed Jordan's former foreign minister, Abdelilah al-Khatib, as his special envoy to Libya, adding that Libya had agreed to accept the immediate dispatch of a humanitarian assessment team to its capital.