Libyan forces loyal to Muammar Gaddafi struck hard at rebels advancing towards Tripoli and pounded the oil port eastern city of Ras Lanuf, as the US mulled land and air options amid growing pressure to arm the out-gunned opposition.
Pro-Gaddafi troops used fighters, gunships, tanks and heavy artillery to hold back the movement of the rebels towards his bastion Tripoli and used artillery and rockets to target them in Bin Jawad, Tobruk, Ras Lanuf and Misurata, Al Jazeera channel said.
It said there was fierce fighting in Misurata, located between Tripoli and Gaddafi's hometown Sirte, with reports of at least 18 people killed.
Meanwhile, Jordan's former foreign minister Abdul Ilah Khatib, on Sunday was named as UN special envoy for humanitarian affairs in Libya.
UN spokesman Martin Nesirky, announcing Khatib's appointment Sunday in New York, said he would have 'urgent consultations' with Gaddafi's government and work on the humanitarian crisis.
Khatib, 56, will leave for New York "in the next few days before travelling to Libya, where he should meet with all parties involved in the conflict," a source added.
"For a few days the rebels were making gains, but overnight it would appear that pro-Gaddafi forces took some ground," the Arab channel said.
The see-saw battles between the rebels, seeking the ouster of the Libyan leader who has ruled for 41 years, and loyalists entered the 21st day, amid global concerns that the fighting could drag for months.
The New York Times said the US military had prepared a blue print of land, air and sea options in Libya in case Washington and its NATO allies decide to intervene there.
"Euphoria in anti-government strongholds is fading as Gaddafi's forces draw line in sand on roads to key city of Sirte," al Jazeera reported from the frontline. Sirte is the hometown of the Libyan leader, who has made it a prestige to hold it.
Eight deaths including six rebel fighters were killed in the battle of Bin Jawad.
"For a few days the rebels made gains, but overnight it would appear that pro-Gaddafi forces are on the offensive and have taken some ground," al Jazeera said. Hard pressed, the rebels are asking for UN backed air strikes as Gaddafi's Russian fighters and helicopter gunships are playing havoc with them.
The rebels also say that Gaddafi is using African mercenaries to suppress an uprising against his rule. In the first overtures to the rebels, the Gaddafi government offered to open talks with them but this was promptly rejected.
UN seeks aid
Geneva: The UN Monday appealed to donors for $160 million to provide humanitarian assistance in Libya over the next three months. The UN said it intends to assist up to 400,000 people who might escape the troubled North African country.
According to the International Organization for Migration (IOM), an inter-governmental agency, some 213,000 people have fled Libya since February 20.