|The western city of Misurata has borne the brunt of bombardment by Gaddafi's forces for almost six weeks [Al Jazeera]
Libya's opposition fighters are battling Muammar Gaddafi's forces on the country's western border, while fighting continues in the besieged city of Misurata.
Pro-democracy forces said the Libyan army withdrew from central Misurata, but fierce fighting was still ongoing for control of the city's port on Wednesday.
"Gaddafi's forces retreated from the port area where they were positioned yesterday after air strikes
by the NATO forces. The strikes completely destroyed 37 military vehicles," an opposition spokesman, called Reda, told the Reuters news agency.
"Gaddafi's forces this morning started bombarding an area about 10km north of the city. It is known as the Steel area.
"The bombardment is still going on. They are using Grad missiles ... Warplanes are flying over Misurata's outskirts but I don't hear any sound of strikes," he said by telephone.
While government forces pulled out of the city over the weekend under pressure from NATO air attacks, they have since unleashed a heavy bombardment on the city, the only major western city in opposition hands.
"Another development which is rather disturbing is that there has been shelling in the docks area, which is the lifeline to opposition forces and indeed the civilian population here," Al Jazeera's Andrew Simmons reported from Misurata.
"Reports from an opposition spokesperson say pro-Gaddafi troops are intent to cut the main road from city to the port. If the lifeline is cut then everyone is in a desperate situation.
"Though Gaddafi troops have left the city everybody is under threat of shellfire. The whole city centre has been destroyed and needs to be rebuilt."
Migrant workers stranded
Amid the tension, thousands of migrant workers have been left stranded in Misurata, waiting for relief organisations to ship them to safety.
One ship sent to evacuate a thousand migrants from the city docked on Wednesday in the port after spending a night offshore awaiting a lull in shelling, the aid agency International Organisation for Migration (IOM) said.
It said at least one migrant from Niger was reported killed and up to 20 others wounded in the bombardment of Misurata a day earlier.
At least 1,500 migrants, most from sub-Saharan Africa including Niger and Chad, have gathered at the port some 10-12 kms east of the city awaiting rescue, the group said.
It said tens of thousands of migrants, mainly from sub-Saharan Africa, have fled the conflict in Libya into northern Niger and Chad, and are in need of urgent support.
Fears of stalemate
With fears of a stalemate in the Libyan conflict looming, Liam Fox, British defence secretary, met Robert Gates, the US defence secretary, in Washington on Tuesday.
"We discussed how situation is progressing. Thanks for Predator drones made available by the United States. Also there has been progress in Misurata and the Gaddafi regime is on the back foot," Fox said.
"We've seen some momentum gained in the last few days."
Libya, for its part, has urged Russia to call an emergency meeting of the UN Security Council to discuss what it called "Western aggression".
Vladmir Putin, the Russian prime minister, has criticised the NATO-led coalition no-fly zone over Libya and said it had no mandate to kill Gaddafi.
'Gaddafi not targeted'
However, the US defence secretary said the coalition was not targeting Gaddafi specifically, despite hitting one of his compounds with a recent air strike.
"The same values and principles apply to all countries. Our response to each country has to be tailored on the prevailing situation in each country," Gates said.
"There was a degree of international support for the Libya air strikes. The Arab League passed a resolution in support of no-fly zone and later the UN also backed it."
Meanwhile, US senator John McCain, the highest profile American politician to visit Libya since the start of the conflict, called for the use of more air power to prevent what he called a humanitarian crisis in Libya.
"If you are really in this to prevent a humanitarian disaster, the only way you can prevent it is to have Gaddafi not able to inflict it," McCain told Al Jazeera.
US Senator John McCain, who recently visited Benghazi, advocates the use of air power in Libya [ Al Jazeera]
Meanwhile, the Obama administration has eased its sanctions against Libya to allow for the sale of oil controlled by the rebels. The move will allow Libya's opposition forces to use the income from oil sales to buy weapons and other supplies.
The US also ordered the expenditure of up to $25 million in surplus government goods to support Libyan opposition groups and protect civilians threatened by Gaddafi forces.
In a related development, Italy said it would join the British and French in carrying out bombing attacks on Libya.
Geographically the closest major NATO member state to Libya, Italy had until Monday only provided bases and reconnaissance and monitoring aircraft. The rebel-led the Libyan National Transitional Council [NTC] welcomed the Italian decision.
Separately, Italy and France called on the international community to stop shipping oil products to the Libyan government and urged market operators not to buy its crude oil.