BENGHAZI, Libya/TRIPOLI (Reuters) - Eastern Libyan military forces have moved to western Libya and were briefly locked in a skirmish with a rival force south of the capital Tripoli, an eastern official and residents said on Wednesday, in an escalation between rival camps in the oil producer.

FILE PHOTO: Members of forces loyal to Libyan military commander Khalifa Haftar guard near Libya's El Sharara oilfield in Obari,Libya, February 6, 2019. REUTERS/Stringer

The advance took diplomats and analysts by surprise, exploiting their focus on neighboring Algeria where President Abdelaziz Bouteflika resigned on Tuesday after protests, to the relieve of Western countries valuing stability there.

Libya -- in trouble since the overthrow of Muammar Gaddafi in 2011 -- is divided between the internationally recognized government in Tripoli and a parallel administration allied to Khalifa Haftar.

Haftar has turned into major player in the North African country, enjoying the backing of Egypt and the United Arab Emirates which see him as bulwark against Islamists. His opponents see in him a new Gaddafi.

His forces control the east and recently expanded to southern Libya.

Now in a new escalation Haftar’s Libyan National Army (LNA) moved in the past days discreetly forces west with the LNA media office publishing on Wednesday videos of troops traveling on a coastal road from Benghazi, the main eastern city.

In the evening a brief skirmish lasting one hour was reported near Gharyan, a town south of Tripoli between the LNA and forces allied to Tripoli Prime Minister Fayez al-Serraj, who relied on patches of armed groups with flexible loyalties.

“Right now they are clashes south of Tripoli...in Gharyan,” LNA spokesman Ahmed Mismari told al-Arabiya channel.

No casualty figures were or details were immediately available.

There was no immediate comment from the Tripoli government, which had issued earlier a general alert for its forces in response to the eastern advance.

“There is no military solution,” Serraj said in the statement.

OFFENSIVE?

Analysts doubt the LNA is capable of launching a full-scale attack as it has stretched itself with the southern advance and it also relies on tribesmen and other auxiliary forces.

Some diplomats say the advance is mainly a psychological campaign to pressure Serraj into a power-sharing deal on eastern terms, allowing Haftar to become commander of a national army.

The confrontation is in any case a major setback for the U.N and Western countries which have been trying to mediate between Serraj and Haftar. Both men had met in Abu Dhabi last month to discuss a power sharing deal and a national conference is set to follow this month to agree on a road map for elections.

Some of Haftar’s supporters have called the U.N. efforts a waste of time, urging him to carry out a military solution to establish himself as national army commander.

During the day the LNA had turned up pressure on Tripoli, warning of a military campaign to “liberate the homeland from terrorism”.

“We expect the women of Tripoli to welcome the Libyan army like the women of Benghazi and Derna did,” said Mismari, referring to two eastern cities which the LNA took by force.

Mismari also called on young people in Tripoli to focus on the battle between LNA and Daesh, or Islamic State, in another hint that military action might be looming.

The comments suggest the LNA might seek to takeover Tripoli working with local groups instead of seeking an invasion.

In January, the LNA, which is loyal to Haftar, started a campaign to take control of the south and its oilfields with a similar rhetoric.

The announcements coincided with the arrival in Tripoli of U.N. Secretary General Antonio Guterres who is on a regional tour seeking to help avoid a confrontation between the rival Libyan camps.

On another potential frontline, a resident in Ras Lanuf, an oil town located on the coastal road, said tanks and military convoys were seen heading westwards in the direction of Sirte.

Sirte is in central Libya controlled by a force from the western city of Mistrata allied to the Tripoli administration.

Misrata, a port east of Tripoli, is home to powerful armed groups, which could match at least partly the firepower of LNA ground troops, analysts say. Haftar’s forces enjoy air superiority.