TRIPOLI, May 4 (Xinhua) -- Libya's UN-backed government on Saturday held the east-based army responsible for the return of Islamic State (IS) to southern Libya, following a deadly attack carried out by the terrorists in the southern city of Sabha against an army training center.

"The (government's) Presidential Council holds Haftar (army commander) directly responsible for the return of IS to its activity, after the services of government of national accord managed to eliminate the organization and pursue its remnants and sleeper cells," the government said in a statement.

"Haftar left his forces in chaos in the south, after he claimed that his war there aimed to eliminate terrorism," the statement added.

The government also condemned the attack, offering condolences to the families of the victims.

IS claimed responsibility for an attack on an army training center in the southern city of Sabha, killing nine soldiers.

Sabha, southern Libya's largest city, has been under the control of the east-based army, led by General Khalifa Haftar, since January.

The army, led by Haftar, has been leading a military campaign since early April to take over the capital Tripoli from the government.

The fighting so far killed nearly 400 people, injured almost 2,000 others, and forced more than 50,000 people to flee their homes.

Libya has been suffering escalating violence and political division ever since the fall of the late leader Gaddafi's regime in 2011.