WADI DINAR, Libya - Many revolutionary fighters are abandoning one of the main fronts in the battle to rout Moammar Gadhafi's loyalists, saying they're not afraid of dying in the face of heavy resistance but are tired of the disorganization and lack of ammunition among their own ranks.

Bani Walid has proven impenetrable in part because of its daunting natural defences -- the town of 100,000 is strung along mountain ravines where loyalists hold the high ground. But the nearly month-old assault has only underscored the disarray in the forces of Libya's new rulers, which include both a relatively organized military and brigades of untrained volunteers.

The regular forces have already pulled back from the Bani Walid siege to focusing on Gadhafi's hometown of Sirte, further east on the Mediterranean coast, and other strongholds further south.

Weeks after Tripoli fell and Gadhafi went into hiding, revolutionary forces have struggled with his loyalists' strongholds in Bani Walid and Sirte. Further south deep in the desert lies another bastion, Sabha, and several desert towns in between remain in the hands of the ousted regime -- an obstacle as the country's new ruler, the National Transitional Council, tries to solidify its control.

In recent days, even the volunteer fighters who had remained at Bani Walid, determined to continue, have begun to filter away in frustration.

Mohammed Andar, a 35-year-old former police officer, said he decided to return to his home in Zawiya after he was wounded by shrapnel in the back of his leg in an ambush on his brigade. He was being rushed to the hospital Wednesday, the same day his twins celebrated their first birthday.

His wounds were not serious enough to keep him from battle, but he felt it was pointless.

"A martyred father would be an honour for my children, but not in this chaotic, ill-planned way," he said while resting near a revolutionary checkpoint about 25 miles (45 kilometres) north of Bani Walid.

To enter Bani Walid from the northwest, coming from Tripoli, the revolutionary fighters must cross a steep valley, some 400 yards (meters) wide, that divides the city. Gadhafi loyalists hold the high ground on the other side, enabling them to rain down with rockets, mortarts and cluster bombs on fighters trying to approach the valley.

Osama al-Fasi, a field commander from Bani Walid, said his fighters were not prepared for such fierce resistance and blamed the NTC's military leadership for not providing the necessary ammunition, weapons and leadership to sustain a real attack on the city.

"We were shocked at the force of the resistance we faced," al-Fasi told The Associated Press, referring to Gadhafi loyalists as garbage. "Bani Walid is filled with the garbage of Libya and we don't even have heavy weapons to fight them with."

On Friday, leaders of al-Fasi's brigade, the Martyrs of 28 May, decided to officially abandon the northern front and move their base to the southern front because the terrain is easier to fight through.

Five Russian tanks made in the 1970's and seized by fighters when Tripoli fell last month arrived in Wadi Dinar at the revolutionaries' positions on the city's northern outskirts last week, but have sat idle in desert checkpoints requiring maintenance. Fighters spend their days lounging on them, posing for photos from cellphones and using them to dry laundry.

"Can you believe that I enter the front line here with only one magazine for my Kalashnikov?" Hassan Abdel-Qadir, another fighter from the city of Zawiya, east of Tripoli, said in disbelief. "We feel very deflated and frustrated -- where is the military council with its leaders and ammunition and help? We've been left to fend for ourselves here."

Military rebel commander Daw Saleheen said it was impossible for the army to inform everyone of movements or information because the resources were not available.

"There are so many fighters and we can't communicate to all of them," he said. "This is a revolution -- of course it's going to be chaotic."

Andar said the lack of communication was proving fatal.

On Wednesday, a number of leaderless fighters attempted to push the northernmost checkpoint deeper into the city and enter the centre via off-road routes.

Abdel-Salam Genouna planned the attack, which backfired when Gadhafi loyalists armed with heavy machinery ambushed the 10 cars on the expedition from hidden valleys, killing eight fighters, according to Alaa Shafori, a doctor at a field hospital.

"We ran out of ammunition because we were just planning to make this a patrolling expedition," he said. "It was a shock and we are lucky many of us survived."

The remaining fighters have been left shell-shocked and uncertain if Bani Walid is worth the fight.

"I want to die for Libya and for freedom, not for this kind of mess," said Bassam Turki, a 33-year-old fighter from Tripoli who went home after last week's battle.

Fighters besieging Gadhafi's hometown of Sirte, further east on the Mediterranean coast appear much more organized, though they too have faced stiff resistance. On Saturday, they pushed into the western side of the city under heavy fighting. They have also moved around the city to try to cut off supply lines through the desert to the loyalists.

Andar, the former police officer who quit the fight at Bani Walid, said tribal loyalty also was proving stronger in the city than other areas, making it harder to gain local support for the revolution.

"In all the cities we liberated, the people inside the city rose up and helped us -- except in Bani Walid," Andar said.

Field commander Fathi Kirshadz said the Bani Walid forces had been diminished because local fighters were worried about their families and defected.

Al-Fasi said he was a wanted man inside Bani Walid. He said Gadhafi forces have his name as well as a number of other Bani Walid fighters on a "wanted for execution" list and were attacking their families.

The fighters are too week to hold positions inside the city, making families that raise the tri-colour revolutionary flag vulnerable. Al-Fasi said sources inside Bani Walid have told him about 15 civilians have been killed in raids since last Friday.

"We are responsible for the souls of those dead civilians," al-Fasi said, putting his hand to his neck. "Those families greeted us with celebration, and we left them to die."