(Updates death toll, adds details)
By Ali Shuaib
TRIPOLI, Feb 13 (Reuters) - At least five people have been killed in clashes between rival tribes over control of territory in the far southeast of Libya, officials said on Monday, highlighting the challenge of policing the country's sparsely populated desert.
Violence broke out on Sunday in the remote city of Al Kufra and continued into Monday.
Libya's National Transitional Council has struggled to assert its authority across the whole of Libya as rival regional militias and tribal groups jostle for power and resources following the fall of Muammar Gaddafi.
Local gunmen from the Zwai tribe clashed with fighters from the Tibu ethnic group led by Isa Abdel Majid, whom they accuse of attacking Al Kufra backed by mercenaries from Chad, Abdelbari Idriss, a security official from the Zwai tribe, told Reuters.
Abdel Majid's men, who supported the Libyan rebels during the 2011 uprising that ousted Gaddafi, had set up camp in Jalu north of Al Kufra on Sunday and were holding out there, Idriss said, but another source said fighting was still going on.
Farhat Abdel Karim Bu Hareg, coordinator of Social Affairs in the local government of Al Kufra, criticised the NTC for neglecting the southeast though Al Kufra province is Libya's largest and straddles the borders of Sudan and Chad.
He said the region would be forced to declare independence unless it received support to end what he said were attacks by mercenaries. "I would like to reiterate that if no response is made to rescue the people, we will be forced to declare our independence".
Local fighters have called for help from Benghazi and Misrata but had yet to receive any response, he said. The roads in the region are poor while some reports suggested said the airport was out of use due to the fighting, possibly holding up any aid.
Bu Hareq said Chadian and South Sudanese fighters from Darfur were involved in the fighting and the situation had deteriorated after a local military barracks came under attack.
"Around 40 4x4 vehicles carrying soldiers attacked a military camp known as May 5 and the wounded persons number in the hundreds," Bu Hareg said.
The Tibu are mainly found in Chad but also inhabit parts of southern Libya, Sudan and Niger often crisscrossing unmarked desert borders. It was not immediately possible to contact Abdel Majid for his comments on the origins of the clash and fighters.
In Al Kufra, tribal ties are far more powerful than they are on the country's Mediterranean seaboard. A tribal rebellion in 2009 was suppressed only after Gaddafi sent in helicopter gunships, while in 2011, Sudan sent in weapons to help Libyan rebels wrest control of the area.
The remote region is also a hub for smugglers taking advantage of the lawless borders of sub-Saharan Africa.
Writing by Lin Noueihed; Editing by Giles Elgood