That toll includes only victims from among tribal groups who have been fighting armed members of the Toubou tribe in the desert city 750 kilometres (465 miles) south of the capital.
Toubou chief Issa Abdel Majid Mansur has spoken of 40 members of his tribe killed, and accused the Libyan authorities of using warplanes and tanks against Toubou positions in the south of Sabha city.
Speaking to AFP, Mansur denounced what he said was a plan to "ethnically cleanse" his people, and raised the threat of a separatist bid.
"We announce the reactivation of the Toubou Front for the Salvation of Libya (TFSL, an opposition group active under the former regime) to protect the Toubou people from ethnic cleansing," Mansur said.
"If necessary, we will demand international intervention and work towards the creation of a state, as in South Sudan," he said.
Abdelrahman Seif al-Nasr, security chief of the southern Fezzan region, told AFP on Monday that the fighting pitted Toubou tribesmen and Sabha residents.
Ali al-Dib, a former rebel, said the clashes erupted in the city centre when the Toubou refused to hand over to local authorities one of their men accused of killing a member of the Bussif tribe.
Colonel Mohammed Bussif, head of national security in Sabha, has spoken of a "dramatic situation" there, and pointed the finger of blame at "outlaws backed by elements from outside the country."
"The situation is very bad," Bussif told Libya's Al-Hurra television channel.
Sabha's representative on the ruling National Transitional Council (NTC) told the broadcaster he was stepping down from his post to denounce government "passivity" and its "incapacity to react" to the situation.
Mansur, formerly an opposition activist against the regime of Moamer Kadhafi, had announced the dissolution of the TFSL after the slain dictator's regime fell.
"It turns out that the National Transitional Council and the Kadhafi regime are no different. The NTC has a programme to exterminate us," claimed Mansur, whose people played a key role in the south during last year's revolt.
"We have already said that the unity of Libya was above every other consideration. But now we have to protect both ourselves and other minorities," Mansur told AFP.
The Toubou are oasis farmers by tradition who also have connections beyond Libya's borders.
They live in southern Libya, northern Chad and in Niger, and have previously denied having separatist ambitions.
Ruling NTC member Mukhtar al-Jadal said on Monday that NTC chief Mustafa Abdel Jalil had met representatives from the south in an effort to broker a solution to the crisis.
A local source said Toubou tribesmen who had been in "brigades of former rebels have defected and rejoined their own" people, adding that "some elements from Chad are fighting with the Toubou."
The Toubou have also been involved in deadly clashes with another tribe in the Saharan oasis of Kufra, where two ethnic groups are locked in a standoff over smuggling.
Despite an army-brokered truce, tensions still simmer in Kufra, where clashes between the Toubou and the Zawiya and other groups claimed more than 100 lives during a fortnight of violence in February.
The triangle bordering Chad, Egypt and Sudan is a key transit route for the trafficking of goods of all kinds, both legal and contraband -- alcohol, cigarettes, counterfeit goods, drugs, weapons and especially illegal immigrants hoping to reach Europe.
-------------------------------------------------------------------------------------------------