SIRTE (Reuters) - Libya's new rulers have said they believe fugitive former leader Muammar Gaddafi is being shielded by nomadic tribesmen in the desert near the Algerian border, while his followers fend off assaults on his hometown.
Intense sniper and artillery fire from pro-Gaddafi fighters has so far prevented National Transitional Council (NTC) forces from taking Sirte despite more than two weeks of fighting.
One of Gaddafi's last two bastions, it has withstood a siege, NTC tank and rocket fire as well as NATO air strikes. The United Nations and international aid agencies are worried about conditions for civilians trapped inside.
More than a month since NTC fighters captured the capital Tripoli, Gaddafi remains defiantly on the run pledging to lead a campaign of armed resistance against the new leaders.
Gaddafi himself may be holed up near the western town of Ghadames, near the Algerian border, under the protection of Tuareg tribesmen, a senior NTC military official said.
"There has been a fight between Tuareg tribesmen who are loyal to Gaddafi and Arabs living there (in the south). We are negotiating. The Gaddafi search is taking a different course," Hisham Buhagiar told Reuters, without elaborating.
Many Tuaregs, nomads who roam the desert spanning the borders of Libya and its neighbours, have backed Gaddafi since he supported their rebellions against the governments of Mali and Niger in the 1970s and allowed them to settle in Libya.
Buhagiar said Gaddafi's most politically prominent son, Saif al-Islam, was in the other final loyalist holdout, Bani Walid, and that another son, Mutassem, was in Sirte.
Lack of coordination and divisions at the frontlines have been hampering NTC attempts to capture Sirte and Bani Walid.
Fighting continued on separate eastern and western fronts in Sirte on Wednesday and commanders said they would try to join the two fronts together and take the city's airport.
"There is progress toward the coastal road and the airport.... The plan is for various brigades to invade from other directions," NTC fighter Amran al-Oweiwi said.
Street-fighting was under way at a roundabout 2 km (1.5 miles) east of the town centre, where anti-Gaddafi fighters were pinned down for a third day by sniper and artillery fire.
As NATO planes circled overhead, NTC forces moved five tanks to the front but were immediately met with Grad rockets fired from inside the town, missing the tanks by only yards.
A Reuters crew at the scene saw some NTC fighters flee the frontline under heavy fire while others stood their ground.
Civilians continued to flee from Sirte.
"There is no fuel, no electricity and there are shells flying everywhere," resident Mohammad Bashir, who left Sirte on Wednesday, said at a checkpoint just outside the city.
He said that most pro-Gaddafi fighters in Sirte were volunteers. "Some tried to stop us from leaving and some of them will shoot at you," Bashir said.
Medical workers said 15 fighters were killed in Sirte on Tuesday, the highest single-day death toll. Two more, including a senior NTC field commander, were killed on Wednesday. More than 100 fighters were wounded, many from sniper fire.
NTC fighters captured 60 African mercenaries in Sirte on Wednesday. They said most had come from Chad and Mali to fight with Gaddafi loyalists.
As the fighting continues, humanitarian organisations are sounding the alarm about the possibility of civilian casualties in the town. Gaddafi's spokesman has said NATO air strikes and NTC shelling are killing civilians.
NATO and the NTC deny that. They say Gaddafi loyalists are using civilians inside Sirte as human shields and have kidnapped and executed those they believe to be NTC supporters.
Four civilians were wounded when a shell fell on a house on the eastern outskirts of Sirte on Wednesday. Medical workers evacuated the four men to a hospital in Ras Lanuf, which lies 220 km (137 miles) east of Sirte.
"We were sitting in the house, making tea, and all of a sudden a rocket landed," said Ali Al-Ferjani, adding that he believed the shell was fired by Gaddafi fighters.
Additional reporting by William MacLean and Alexander Dziadosz in Tripoli, Emad Omar in Benghazi, Samia Nakhoul in London, Christian Lowe and Hamid Ould Ahmed in Algiers; Writing by Barry Malone and Joseph Nasr; Editing by Myra MacDonald