Libya's interim government on Saturday announced a ceasefire aimed at ending six days of deadly tribal clashes in a southern desert oasis that cost more than 150 lives.

"We announce that reconciliation efforts have resulted in an accord on a ceasefire," premier Abdel Rahim al-Kib told reporters in the capital, adding that "calm now prevails in Sabha," 750 kilometres (465 miles) to the south.

At least 16 people were reported killed on Saturday alone in and around the oasis city before the truce deal was announced.

The fighting between Toubou fighters and Arab tribesmen erupted on Monday after Arab tribesmen accused the Toubou of killing one of their own.

Kib held a joint news conference on Saturday with Yussef al-Mangush, chief of staff of the new Libyan national army that is currently being formed, defence minister Osama Juili and health minister Fatima al-Hamrush.

"Now the situation is calm, and defence ministry forces are securing strategic zones and installations, notably the airport," Mangush said.

Hamrush gave a toll of at least 147 killed and 395 wounded by late on Friday.

"The number of people killed is 147," she said, adding that the toll included casualties from both sides.

Hamrush said 395 people had been wounded, including 129 who were brought to the capital for treatment.

The toll did not include those killed on Saturday -- eight on either side, according to sources in Sabha.

A doctor at Sabha hospital, treating Arab tribal casualties, said eight people were killed and another 50 wounded in fighting between the early morning and noon. A Toubou tribal source said eight of their people were also killed.

"We haven't slept since yesterday. The Toubou have been attacking Sabha since three in the morning, and they very nearly took the city. All the residents have taken up arms to defend it," Dr Abdelrahman al-Arish told AFP.

Adem al-Tebbawi, a local Toubou official, spoke of eight dead and "several wounded" on his side.

Local sources said Toubou fighters who had been pushed back several kilometres (miles) south of Sabha launched a counter-attack early on Saturday in a bid to re-enter the city.

The first three days of clashes cost more than 70 lives, Libyan government spokesman Nasser al-Manaa said on Wednesday.

Ex-rebel forces dispatched from the north to try to impose a ceasefire and act as a buffer between the two sides failed initially to quell the violence.

Juili said on Saturday a war room had been set up to deal with the situation in Sabha and that aircraft were carrying out reconnaissance missions in the area.

"We will not permit any party to violate the ceasefire," he said.

The Toubou accuse the authorities of backing the other Arab tribes, who in turn denounce government "inaction" and "passivity" in the face of a "foreign invasion" in the absence of an organised national army able to restore order.

Other tribes accuse the Toubou of including foreign fighters among their ranks, notably from neighbouring Chad, a charge the Toubou deny.

"The Arab tribes are stopping African immigrants working in the town and presenting them to the press as Toubou fighters come from abroad," Tebbawi countered.

"We have respected a truce and we want reconciliation, but the other tribes -- especially the Awled Suleiman -- have not stopped attacking us for several days. We have been deprived of both water and power," he said.

On Friday, Toubou chief Issa Abdel Majid Mansur accused Arab tribes in Sabha of bombarding a power station providing electricity to several parts of southern Libya including Qatrun and Morzuk, both areas with a strong Toubou presence.

The former opposition activist against the ousted regime of slain dictator Moamer Kadhafi also called for international intervention to halt what he called "ethnic cleansing" of the Toubou.

The Toubou say they are defending themselves against attack by Arab tribesmen in the region, and have accused the Libyan authorities of backing those gunmen as part of a campaign of "ethnic cleansing."

The Toubou are black 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.