Libyan fighters aligned with the Libyan National Transitional Council (NTC) say battles are continuing for the loyalist stronghold of Bani Walid, a town 50km southeast of Tripoli.
Al Jazeera correspondent David Poort reported from the frontline that Bani Walid was not under control early on Saturday mostly due to active sniper fire from the forces of Muammar Gaddafi.
A day before, Gaddafi's troops fired Grad rocket barrages at the fighters besieging Bani Walid and Sirte, a coastal city also under the deposed leader's control.
Abdullah Kenshil, the NTC's spokesman and chief negotiator, said the anti-Gaddafi fighters were exchanging fire with gunmen positioned in houses in the town of Bani Walid and the hills that overlooked it. "They are inside the city. They are fighting with snipers... They forced this on us and it was in self-defence."
Kenshil said on Saturday that Gaddafi forces in Bani Walid received reinforcements during the night.
Reuters news agency reported that a NATO aircraft carried out at least five air strikes around Bani Walid on Saturday. Anti-Gaddafi fighters retreated from the town earlier on Saturday, saying that they expected a NATO bombardment.
Al Jazeera's Sue Turton reported that there seemed to be more pro-Gaddafi fighters than expected, possibly coming in from Sirte, Gaddafi's hometown. "This is a surprise as it was thought that the rebels had cut off that link between the two towns," she said.
NTC forces also battled loyalists to the east of Sirte on the Mediterranean coast, but were forced to pull back after taking heavy casualties in close-quarters fighting, a spokesman said.
The NTC had given loyalists in Bani Walid and Sirte until Saturday to give up peacefully or face attack, although previous deadlines had been extended to allow more time for negotiations.
Ambulances transferred casualties from Bani Walid, as NTC fighters grabbed crates of rocket-propelled grenades and mortars and raced to the front.
In Teassain, 90km east of Sirte, witnesses told the Reuters news agency they saw heavy rocket exchanges between NTC forces and Gaddafi loyalists.
Kenshil told Al Jazeera earlier on Friday: "I think we are very close. We are pushing further and we hope we can take the city without further fighting.
"But from our experience, they [pro-Gaddafi troops] are fighters - very professional, from different parts of Libya and also mercenaries ... once we engage with them they throw down their weapons. There are snipers who shoot at the troops and at civilians," he said.
"We've entered the area from the east, north and south. The deadline is finished. They [pro-Gaddafi troops] finished it."
Gaddafi's location has been unknown since Tripoli fell to opposition fighters on August 23 after a six-month civil war.
'Worst case scenario'
Gaddafi insisted in a defiant audio message broadcast on Thursday that he was still in Libya to lead the fight against what he called the"rats" and "stray dogs" who had taken over Tripoli.
But four of his senior officials, including his air force commander and a general in charge of forces in south Libya, were among a new group of Libyans who had fled to neighbouring Niger, according to officials in Niger.
General Ali Kana, the southern commander, and Ali Sharifal-Rifi, the air force chief, were among 14 Libyans who arrived in the northern Niger town of Agadez on Thursday after crossing the border in a convoy of four-wheel drive vehicles, they said.
A Reuters reporter in Agadez said the four senior men were staying at the luxury Etoile du Tenere hotel, said to be owned by Gaddafi, who stayed there during a holiday in 2007.
Niger, under pressure from Western powers and Libya's new rulers to hand over former Gaddafi officials suspected of human-rights abuses, said it would respect its commitments to the ICC if Gaddafi or his sons entered the country.
"We are signatories of the [Hague-based International Criminal Court, or ICC] Rome Statute so they know what they are exposed to if they come," Massaoudou Hassoumi, the head of the Nigerien cabinet, said.
He said the latest arrivals were "under control" in Agadez, through which the head of Gaddafi's security brigades, Mansour Dhao, passed earlier this week en route to Niger's capital, Niamey.
"We are taking them in on humanitarian grounds. No one has told us that these are wanted people," Hassoumi said.
Niger, which only this year returned to civilian rule and is fighting al-Qaeda-linked groups in its desert north, fears the Libya conflict might spill over, Hassoumi said.
"We have prepared for a worst-case scenario, for example if Bani Walid and Sirte were to fall by force, it could cause a massive stampede of armed groups into Niger," he said.