A doctor at a regional hospital on Tuesday said that the death toll in violence between ethnic Tabu fighters and gunmen from Sabha - Libya's fourth largest city - had so far reached 34.

"The hospital crew has been working around the clock since Monday night and the injured keep coming in," Ibrahim Misbah told the Reuters news agency.

Later reports put the number of dead at as high as 50, with more than 100 people said to have been wounded.

Colonel Mohammed Bussif, head of national security in Sabha, was reported to have described a "dramatic situation," blaming "outlaws backed by elements from outside the country."

A Libyan Interior Ministry official said 300 soldiers stationed in southern Libya had on Monday been sent to help restore calm, with another 300 having left Tripoli on Tuesday.

Clashes sparked after ex-militiaman killed

Fighting broke out on Sunday between former rebel fighters from Sabha and Tabu gunmen, after a Sabha man, a former rebel from the Bussif tribe, was killed in a dispute over a car.

The head of the Tabu tribe has complained that the clashes are part of a plan to "ethnically cleanse" the region of his people. The Tabu, oasis farmers who also live in neighboring Chad and Niger, have in the past been linked to separatist ambitions.

The incident has been highlighted as the latest example of the ruling National Transitional Council struggling to assert its authority across Libya after last year's rebellion that ousted late dictator Moammar Gadhafi.

rc/dfm (Reuters, AFP, AP)