BENGHAZI - Heavy fighting between pro-Gadhafi troops and rebels broke out in a Libyan city just 160 kilometres east of Tripoli, potentially opening the coastal road to the capital, just as cracks appeared among NATO allies.

Gadhafi forces also shelled for the first time the world heritage-listed city of Gadamis, some 600 kilometres southwest of the capital on the Tunisia and Algerian border, opening a new front in the five-month long civil war.

World powers gave mixed signals on how the deadlocked civil war might play out, with Russia trying to mediate reconciliation. Turkish Prime Minister Tayyip Erdogan said on Friday he had offered a "guarantee" to Gadhafi if he left Libya, but received no reply.

With diplomacy stalling, rebels said fighting was erupting on new fronts.

Ahmed Bani, a military spokesman in Benghazi, told Reuters clashes had broken out in Zlitan on Thursday and resumed on Friday with Gadhafi forces killing 22 rebels.

Zlitan is one of three towns that are under government control between the rebel-held Misrata and the capital and were it to fall could act as a stepping stone to allow the anti-Gadhafi uprising to spread from Misrata, the biggest rebel outpost in western Libya, to Gadhafi's stronghold in Tripoli.

"Large numbers of troops are surrounding Zlitan from all directions and are threatening its residents with having their women raped by mercenaries if they do not surrender," Bani said, adding the rebels controlled parts of the city.

Gadamis Attacked

Rebels also said the oasis town of Gadamis with a population of about 7,000 people, mainly Berber, was under attack after an anti-government protest in the old Roman city on Wednesday.

"Gadamis is being shelled by Gadhafi forces, according to witnesses in the town," spokesman Juma Ibrahim said from the rebel-held town of Zintan in the Western Mountains region.

"This is a retaliation to anti-regime protests," he said.

The old town was de-populated by Gadhafi in the 1990s and its inhabitants moved into modern buildings. It was not clear if the attack targeted the old town, a labyrinth of narrow, underground passages and houses known as the "Pearl of the Desert".

The accounts in Zlitan and Gadamis could not be independently verified and the Gadhafi government did not immediately comment.

In the besieged port city of Misrata, a doctor at the Hekma hospital said 31 people were killed and 110 wounded in government shelling on Friday.