They fired rockets and scored casualties, when they shelled a position of interim government fighters several kilometres (miles) from the city centre.[break]
"They swept the position after targeting us with Grad rockets," said National Transitional Council fighter Omar Ali Ramadan, who said he and others had managed to take cover at an abandoned house.
"At least seven rockets hit our position."
An AFP reporter saw at least three wounded people being carried in to a field hospital, one of whom subsequently died amid cries of Allahu Akbar (God is greatest).
In Bani Walid, another AFP reporter quoted medical and NTC sources as saying six NTC fighters were killed on Friday and 20 wounded in the oasis town, 180 kilometres (110 miles) southeast of the capital.
The NTC said its fighters had entered Bani Walid, but they made a "tactical withdrawal" on Friday evening due to sniper fire.
"It is useless to hold on to positions overnight in a hostile environment," a commander had told AFP.
In Sirte, NTC forces swept further into the city before retreating under heavy artillery fire after two hours of clashes. At least 6,000 fighters battled in and around one of the ousted Kadhafi´s final strongholds.
"The situation at the roundabout is pitiful. There is no central command, we are retreating to regroup and re-enter again from three fronts," said Al-Dhahira Brigade commander Saleb Abu Shaala.
Abu Shaala said the clashes erupted at about 10:30 am (0830 GMT) and that Kadhafi´s forces used heavy artillery and rockets against them.
Doctors at a field hospital reported at least 10 killed and 40 wounded in the fighting in Sirte.
Commander Salem Jeha, a member of Misrata Military Council, told AFP that "we are now concentrated in a handful of buildings in the city and on the outskirts including Wadi Abu Hadi, where Kadhafi´s forces are concentrated."
He said NTC combatants seized Sirte airport late on Friday, a claim disputed by one fighter, and added that there was "no possibility for them (Kadhafi´s forces) to continue their resistance."
Abdel Nasser al-Sheikh, also of the Misrata Military Council, charged that Kadhafi troops "are firing from the Bin Hamal mosque. We cannot attack this place."
"There is progress but snipers remain a problem," said fighter Fatha Allah.
"We reached up to the city centre but there are families there."
Front-line fighters and commanders gave contrasting reports of progress in Sirte, with men on the ground acknowledging they were facing a tough enemy and those in charge downplaying the pockets of resistance.
"We don´t even have five percent of Sirte because we just go in and out," said fighter Abdul Rauf al-Mansuri.
He said that despite the massive deployment of armed vehicles in and around the town only a minority of the men were doing the heaviest of the fighting.
"Only ten cars with men go in at a time while hundreds hang back away from the front line shouting God is greatest," he said.
Mansuri added that after night-time clashes NTC forces did not control the airport and that they had also lost their advantage by pulling back at night, giving Kadhafi´s men time to rearm.
While the former rebels gained major political victoris on Friday with an easing of UN sanctions and receiving Libya´s UN seat, they have yet to dominate the battlefield completely.
Jeha told AFP there were some 1,200 NTC armed vehicles and thousands of fighters, mostly from Misrata, in the Sirte area.
"There may be houses and pockets of resistance, but they will not be able to overcome the rebels´ massive forces," he said, adding that he had received reports that half of the city´s civilians had fled.
Jeha added: "This matter is sealed, it´s over. Our focus will now shift to free the south."
Western nations that were at the forefront of the push for sanctions and help for the rebels hailed the "historic" double breakthrough at the UN for the NTC.
British Foreign Secretary William Hague said it showed the international community´s determination to support a "free future" for Libya.
The Security Council unanimously passed a resolution to ease an assets freeze and arms embargo against Libyan companies and the new government.
It maintained sanctions against Kadhafi and a no-fly zone which has been used to justify NATO air strikes against his forces.
Security Council resolution 2009 also established the UN Support Mission in Libya (UNSMIL) to go to Libya to help the interim government arrange elections and write a new constitution.
The resolution eases sanctions against major enterprises such as the Libyan National Oil Corp, the central bank and the Libyan Investment Authority sovereign wealth fund in a bid to kick-start the economy.
The Security Council also expressed concern at the "proliferation of arms in Libya and its potential impact on regional peace and security."
However, the resolution allows arms supplies and technical assistance to the transitional government for the security of the authorities and for the protection of UN personnel, media and aid workers in Libya.
The Security Council passed resolutions in February and March allowing for sanctions and measures to protect civilians.
While agreeing to keep the no-fly zone in place, Russia´s UN envoy Vitaly Churkin demanded that it be quickly reviewed, renewing accusations that NATO has acted outside the UN resolutions.
Earlier, the UN General Assembly voted to let the interim government take up Libya´s UN seat.
That will allow NTC leader Mustafa Abdel Jalil to attend next week´s UN gathering in New York, where he will meet US President Barack Obama and other world leaders on the sidelines of the General Assembly.
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