PROFILE-Libya's PM was embattled even before his brief capture

* Zeidan presides over increasingly lawless state

* Former diplomat and Gaddafi opponent helped rebel cause

* Criticised over crippling strikes, unrest in oil industry

By Lin Noueihed

Oct 10 (Reuters) - Even before he was briefly snatched by an armed group on Thursday, Libyan Prime Minister Ali Zeidan had cut an isolated figure, struggling to fend off Islamist rivals and stamp his authority on an increasingly lawless state.

A former diplomat, Zeidan defected in the early 1980s to become a long-time exile and outspoken critic of Muammar Gaddafi, involved for a time with a now-defunct dissident group called the National Front for the Salvation of Libya.

He was living in Geneva when the 2011 rebellion against Gaddafi broke out. As a member of the National Transitional Council, Libya's opposition government-in-waiting, he helped to win the rebels international recognition that ultimately led to backing for the war that toppled Gaddafi later that year.

Running as an independent, Zeidan won a seat in Libya's parliament when the country held its first post-Gaddafi election in 2012 though he later lost a race to lead the house.

But with support from the National Forces Alliance, the main liberal force in Libya's parliament, Zeidan was elected prime minister in a televised count on Oct. 14 2012, a week after the last prime minister was dismissed in a vote of no confidence.

Though Zeidan is considered a liberal, he was able to clinch parliamentary backing for his government lineup by including both liberals and members of the Justice and Construction Party (JCP), the political arm of the Muslim Brotherhood.

During his year in office, however, Zeidan has faced growing pressure from Islamists and independents displeased with his handling of an unprecedented wave of strikes by oil workers and armed guards that has paralysed the country's oil production and led to billions of dollars of lost revenues.

As the country's post-Gaddafi woes worsened, with the weak central government struggling to contain rival tribal militias and Islamist militants, analysts said he has looked increasingly isolated, lacking a tribal base and relying mainly on government largesse to appease strikers and other critics.

UNDER PRESSURE

The former rebel militiamen who captured him on Thursday were angry at the weekend capture by U.S. special forces of a Libyan al Qaeda suspect in Tripoli, appearing to hold Zeidan responsible.

"This could be the opening salvo in a coup attempt against Zeidan or it could be a demonstration of discontent with his rule," said Geoff Porter, of North Africa Risk Consulting.

"It fits a pattern in Libya where a group takes a person or facility hostage and use them to negotiate their demands."

Zeidan, who is in his early 60s, has faced repeated demands to step down from Islamists and other critics of his rule.

In September, JCP head Mohammed Sawan told Reuters that Zeidan should resign after failing to tackle corruption or build a unified army in a country riven by regional rivalries.

Sawan said there was growing support within the 200-member assembly for a vote of no confidence in Zeidan's government while the JCP was considering withdrawing its five ministers from his cabinet.

JCP's secular and liberal rivals say the Islamists, whose main strongholds are in coastal cities such as Misrata, have grown in influence in a parliament that was assuming more executive powers and influence in state institutions.

"He makes a tired and somewhat lonely figure in his office - I saw this again when I met him there ... having shouting matches with people on the phone who then ... want to continue to pursue their own route, despite what the prime minister has said," a diplomatic source told Reuters last month.

Zeidan's brief capture by a semi-official armed force loyal to his political opponents, analysts say, will only make it harder for him to govern.