Clashes pitting tribesmen against a peacekeeping brigade in southeast Libya left two people dead and four others wounded, according to local sources.
"The situation is bad," Toubu tribe leader Issa Abdelmajid Mansur told AFP in reference to fresh fighting in the desert town of Kufra.
"We are being attacked by the Shield Libya brigade... until now we have two dead and one person wounded," in our ranks, he said, pinning responsibility for the "siege" on the ruling National Transitional Council.
There was no immediate confirmation of Mansur's toll.
Wissam Ben Hamid, head of the Shield Libya brigade, said that fighting erupted after Zwai tribesman shot dead a Toubu man.
"The Toubu reacted by firing on every car passing near their neighbourhood," Hamid told AFP, adding three of his men were wounded.
Signup to our newsletter and follow us on Facebook and Twitter!
"We asked them to pull back in vain," he continued.
"Clashes with medium weapons are underway," Hamid said.
Colonel Fradj Buchaala, a local representative of the ministry of defence, also confirmed that there was fighting in the town without entering details.
In February, clashes pitting Toubu against Zwai tribesmen in Kufra cost more than 100 lives and displaced half the population, according to UN figures.
Libya's nascent army intervened by sending a brigade of former rebel fighters to uphold a hard-won ceasefire between the two camps.
Kufra, a town of about 40,000, is located in a triangle where the borders of Egypt, Chad and Sudan meet.
The Toubu, who are dark-skinned and present in southeastern Libya as well as in Chad, Sudan and Niger, faced discrimination under the regime of former Libyan leader Moamer Kadhafi.