|Up to 60 people have been injured in Misurata each day as rebels have fought to gain control of the city [GALLO/GETTY]
Khaled Kaim, Libya's deputy foreign minister, says pro-government forces will withdraw from the besieged city of Misurata, leaving the tribes to deal with the rebels.
"The situation in Misurata will be dealt with by the tribes around Misurata and Misurata's residents and not by the Libyan army," Kaim told journalists late on Friday.
"We will leave the tribes around Misurata and Misurata's people to deal with the situation, either using force or negotiation."
Kaim said the Libyan army, which is loyal to the country's leader Muammar Gaddafi, had been given an "ultimatum" to stop the rebellion in the western city, 200km east of the capital, Tripoli.
"There was an ultimatum to the Libyan army: if they cannot solve the problem in Misurata, then the people from (the neighbouring towns of) Zliten, Tarhuna, Bani Walid and Tawargha will move in and they will talk to the rebels. If they don't surrender, then they will engage them in a fight."
Kaim's announcement appears to mark a shift in tactics by pro-Gaddafi forces in Misurata, which has come under heavy fire for weeks.
Meanwhile, one of the wounded government soldiers captured by rebel forces on Saturday said the Libyan army has been ordered to pull out from Misurata.
Khaled Dorman told Reuters news agency: "We have been told to withdraw. We were told to withdraw yesterday."
Later on Friday, NATO air strikes struck what appeared to be a bunker near Gaddafi's compound in central Tripoli.
Government spokesman Mussa Ibrahim said three people were killed by the "very powerful explosion" in a car park near Gaddafi's Bab al-Aziziyah compound.
Reuters reporters said the area was surrounded by a wall and guarded by watchtowers and soldiers. They saw two large holes in the ground where the bombs had torn through soil and reinforced concrete, to pierce what appeared to be an underground bunker.
Smoke was rising from one of the craters and ammunition crates lay nearby. Ibrahim said the area was disused and the ammunition boxes were empty.
Fears of stalemate
The latest air strikes come as John McCain, a US senator who is one of the strongest proponents in the US congress of American military intervention in Libya, said he was worried the battle between Gaddafi's troops and rebel forces was reaching a stalemate that could "open the door to radical Islamic fundamentalism".
McCain also denied during a visit to Benghazi concerns about the possibility of extremist or al-Qaeda elements fighting alongside the pro-democracy forces, telling Al Jazeera "they [opposition fighters] are my heroes".
Admiral Mike Mullen, chairman of the US military's joint chiefs of staff, offered a similar assessment.
"We're watchful of it, mindful of it and I just haven't seen much of it at all. In fact, I've seen no al-Qaeda representation there at all," he said during a visit to the Iraqi capital, Baghdad.
Mullen acknowledged that the Libyan Islamic Fighting Group, which waged a failed armed uprising against Gaddafi's rule in the 1990s, had "stirred a little bit".
He said air strikes had hobbled Libyan forces, but admitted the conflict was moving into "stalemate" as Gaddafi's troops pressed on with their punishing siege in the western city of Misurata.
Need for transitional government
McCain called on Washington to recognise Libyan rebels' transitional council as the true voice of the Libyan people and transfer frozen assets to them.
He also said that the NATO air campaign should be intensified, adding that Western allies should provide rebels with training, weapons and command-and-control activities to help overthrow Gaddafi.
"I would encourage every nation, especially the United States, to recognise the transitional national council as the legitimate voice of the Libyan people," McCain said.
"They have earned this right and Gaddafi has forfeited it by waging war on his own people."
Al Jazeera's Mike Hanna, reporting from Benghazi, says broader recognition "gives the transitional council a legal standing which it does not at the moment enjoy" along with "extra finance" and "greater political authenticity within Libya itself".
"If the council is recognised as the authentic voice of the Libyan people, then they could receive those funds that have been frozen abroad from the Gaddafi regime," he said.
McCain, who is the first senior politician from the United States to visit Benghazi since the conflict broke out in late February, made the trip to Libya on his own.
An aide said he met rebel leaders including finance chief Ali Tarhouni and armed forces head Abdel Fattah Younes.
The US senator's arrival came close on the heels of the US president approving the use of armed drones in Libya against ground forces for the first time since America handed over the military operation to NATO.
The first armed drone mission since Obama's go-ahead was flown on Thursday, but the aircraft, armed with Hellfire missiles, turned back due to poor weather conditions without firing any of its munitions.
Marine General James Cartwright, vice-chairman of the Joint Chiefs of Staff, said the drones can help counteract the pro-Gaddafi forces' tactic of travelling in civilian vehicles that make it difficult to distinguish them from rebel forces.
"What they will bring that is unique to the conflict is their ability to get down lower, therefore to be able to get better visibility on targets that have started to dig themselves into defensive positions," Cartwright said.
Gates, who publicly expressed scepticism about getting involved militarily in Libya before Obama endorsed the limited intervention, said "the real work" of overthrowing Gaddafi will have to be done by the Libyans themselves.