Clashes between rival tribes in the far southeast of Libya have flared up again, injuring several people, the tribes said Friday, despite Libyan troops intervening to end the fighting.

Dozens of people have been killed in the past two weeks in the city of Al Kufra, near Libya's borders with Chad and Sudan, after a long-standing rivalry between two tribes erupted into violence.

The fighting is a fresh challenge for Libya's new leadership which took over after the overthrow of Muammar Gaddafi last year but has struggled to restore stability, hampered by the lack of an effective national army.

Armed forces chief of staff Youssef al-Mangoush said on Thursday Libyan forces had intervened to end the fighting, in a rare example of the government in Tripoli imposing its authority over the fractious country.

However representatives of the two rival tribes in Al Kufra, the Tibu and Zwai, said clashes had resumed again.

The Tibu looted some houses and stole cars, we had to defend ourselves, Adelbari Idriss, a security official from the Zwai tribe, said by telephone. The army hasn't done anything.

Isa Abdel Majid, who is leading the Tibu fighters, also said fighting had resumed and that Tibu living in the western suburbs of Al Kufra had come under attack. He said people had been injured but did not give a figure.

He said around 100 people on the Tibu side were killed since the clashes began. More than 30 of those died while they were being evacuated by road to hospitals in other towns, he said.

It was not possible to independently verify their comments.

Thursday, some of the wounded were flown to hospitals in the capital Tripoli on board Libyan Red Crescent aircraft. Others have been flown to the eastern cities of Benghazi and Ajdabiyah, officials from the Zwai side said.

Members of the Tibu ethnic group are mainly found in Chad but also inhabit parts of southern Libya. The Zwai tribe accused the Tibu of attacking Al Kufra, backed by mercenaries from Chad. The Tibu said it was they who came under attack.

The region has a history of violence involving tribes. A tribal rebellion in 2009 was suppressed only after Gaddafi sent in helicopter gunships.