|Colonel Ahmed Bani, military spokesman of the NTC, said a 'human tragedy' is unfolding in Bani Walid [David Poort]
Tens of thousands of civilians trapped in areas still held by the forces of Muammar Gaddafi are in increasing danger from heavy fighting and siege-like shortages of food, water and medical care, Libya's National Transitional Council (NTC) has said.
Hundreds of families fled "unbearable" conditions in the Gaddafi stronghold of Sirte on Monday, while the NTC said it had captured the airport and other strategic parts of the southern town of Sabha.
During a news conference in Tripoli, Colonel Ahmed Bani, military spokesman of the NTC, said a "human tragedy" is unfolding in Bani Walid where Gaddafi's forces have put up fierce resistance for nearly a week.
"They have stolen all supplies from the residents of the town and they are shooting everyone who is showing support for the revolutionaries. They show no mercy, not even for woman and children," Bani said.
"For us, this is proof that the Gaddafi forces are trying to destroy the city before it will be liberated."
Al Jazeera's Hashem Ahelbarra, reporting from Tripoli, said NTC fighters in Sabha, located 770km south of the capital, were "confident that in a matter of hours they would control the centre of the city".
"In the punch into Sabha, the anti-Gaddafi forces targeted strategic areas, including the airport, which is some 10km from the city centre," said Ahelbarra.
"[Gaddafi loyalists] have been using similar tactics as in Sirte and Bani Walid. They have taken up positions in urban areas and are using snipers in the very centre of the city to repel the forces."
Al Jazeera's David Poort, reporting from Tripoli, said that the NTC had said that its army had not yet taken Bani Walid because of concern for civilians, difficult terrain and disagreements over battle tactics.
"There are certain tactics and procedures we need to follow to take this town. But Bani Walid is completely surrounded. We are also focussed on saving lives, especially civilians," Bani said.
"Sources tell us that many people in Bani Walid do not know what is going on in the rest of Libya. It is surprising how well Gaddafi's forces managed to cut communications with the outside world."
Bani promised that his fighters would not abandon the people of Bani Walid and that the city would be "liberated" shortly.
"The revolutionaries came to Bani Walid this morning and engaged in a hard battle," Abdullah Kenshil, a senior official in the NTC, told the AFP news agency on Monday.
Kenshil added that negotiations were underway for the evacuation of about 50,000 civilians from the town.
NTC fighters also prepared for another battle to wrest Gaddafi's birthplace of Sirte from his loyalists on Monday as humanitarian groups voiced alarm at the reported conditions within the besieged city.
Residents flooding out of the coastal city said the situation is unbearable, with no electricity or water.
Escaping locals told Al Jazeera that hundreds of people were still trapped in Sirte as fighters sent by Libya's new rulers amassed a number of huge rocket launchers and artillery guns to pound the area.
"There's no electricity, no phone coverage, nothing," resident Ibrahim Ramadan told the Reuters news agency, standing by a car packed with his family as he fled the fighting.
Ramadan, who acts as a community leader, estimated that about two-thirds of Sirte's roughly 70,000 population were still inside the city and an all-out NTC assault was expected.
Residents of Sirte said homes had been destroyed and cars smashed to pieces as disorder spread across the city in the recent days of fighting.
"People are fed up. There are explosions going off everywhere and you don't know where the bullets will come from next," resident Abubakr said as he made his way out of the city.
NTC fighters, who were forced into retreat on Saturday after storming the city, said they were holding off advancing deeper into Sirte or firing heavy artillery for now because they wanted to give residents a chance to leave.
"The problem is that there are some [Gaddafi] brigades preventing them from leaving," NTC fighter Sadiq Atman said as his fellow fighters pieced together an anti-aircraft machine gun on the back of a pickup truck.
"If these families were able to get out, this would be a proper war," he said.
Sirte, 450 km east of Tripoli, along with Bani Walid and Sabha, are the last significant strongholds of pro-Gaddafi forces