At least four Libyan soldiers died when forces loyal to Khalifa Haftar fought with a local armed group as they sought to expand south, military officials said.
Libya has been in turmoil since the NATO-backed toppling of Muammar Gaddafi in 2011, with parallel administrations and armed groups carving the nation into swathes of control.
Friday’s clashes were the first real resistance the Libyan National Army (LNA) faction faced since arriving in the south two weeks ago from its Benghazi stronghold.
LNA officials said clashes began when soldiers left Sabha and arrived in Ghudduwah. It backed troops with air strikes on the “terrorists” and “Chadian mercenaries”, officials said, using a pejorative for Chadian opposition groups active in south Libya.
As well as the LNA fatalities, several soldiers were wounded, officials said. There was no immediate confirmation of the LNA’s version and it was unclear if there were other casualties.
The LNA spent the last two weeks securing Sabha, nominally under the control of the internationally-recognised government in Tripoli but in practice run by local groups including tribes.
The LNA says its campaign is intended to combat Islamic militants and secure oil facilities in the south, which include El Sharara oilfield, Libya’s biggest. It has been closed since December when tribesmen and state guards seized it.
The LNA, whose commander Haftar dominates eastern Libya, is allied to a parallel government in Benghazi that opposes the Tripoli administration.