* Northwestern Mellitah complex shut down since Saturday
* Mellitah a joint venture between state oil company, Eni
* Incident latest violent disruption to sector
By Ali Shuaib and Marie-Louise Gumuchian
TRIPOLI, March 3 (Reuters) - Libya has stopped gas exports to Italy from its Mellitah complex after fighting on Saturday between militias, Libya's National Oil Corporation (NOC) and Italy's Eni said on Sunday.
Libya's defence ministry sent security personnel to secure the complex, about 100 km (60 miles) west of the capital Tripoli, to ensure exports could resume soon, said Abdufattah Shagan, chairman of Mellitah, an NOC-Eni joint venture.
Mellitah supplies Italy with gas through the Greenstream pipeline, which at full capacity pumps at least 8 billion cubic metres. Italy gets most of its gas from Algeria, Russia and Norway, with Libya providing about 10 percent.
"Gas exports have been completely halted," NOC deputy chairman Mustafa Sunalla told Reuters on Sunday.
Saturday's firefight began after an argument between former rebel fighters from nearby Zuwara and others from Zintan over who should guard Mellitah, security officials said, adding the clashes were now over.
Deputy Oil Minister Omar Shakmak told a news conference in Tripoli one person was killed and several injured. Khaled Bukrayat, a member of Zuwara Media centre which compiles local news, said seven people were seriously injured.
It was the latest violent disruption to the energy industry in Libya where protests have shut down oil-export terminals in recent months and in the North African region following January's bloody hostage-taking at an Algerian gas plant.
Thousands of former rebels who fought to overthrow former leader Muammar Gaddafi in 2011 have been employed in a protection force to look after Libyan oil and gas installations.
But in recent months activists and local militia have disrupted operations in Libya's main industry, pursuing goals such as better living conditions or more regional autonomy. In July they forced the closure of three major oil terminals.
This has hurt OPEC member Libya's oil output, which returned to close to pre-war levels of 1.6 million barrels per day (bpd) faster than analysts expected after the 2011 conflict.
Eni said gas flows from Mellitah to Gela, Sicily, had been halted and Italy's industry ministry had been alerted.
Speaking from the complex, where only emergency staff were present, Mellitah's Shagan told Reuters defence ministry vehicles were on their way.
"As soon as they guarantee the security, we will resume exports in 48 hours," he said. Defence Minister Mohammed al-Barghathi told Reuters the armed forces were on their way:
"They are under instructions to allow (former rebels) there to leave and then the army will look after the facility."
Mellitah has two plants - one treating oil and condensate from the Wafa fields and another for gas and condensate from the Sabratha offshore platform, according to Mellitah's website.
A senior Libyan oil official said production at both Wafa and Sabratha had been affected by the Mellitah shutdown.
A Zuwara resident said on Sunday tensions had escalated for days before the dispute. "There were two bouts of fighting yesterday," said the resident, who gave his name as Ayub.
"From what I understand, some of the Mellitah staff were evacuated, others came to Zuwara by boat from there."
In December, protesters seeking jobs and better living conditions shut down the Zueitina terminal for around two months, halting around 60,000-70,000 bpd of oil exports.
While the return of foreign oil companies - including Eni - to Libya helped it increase its output after the 2011 uprising, foreign workers have been slow to return to the country, awash with weapons, because of precarious security.
"Such disruptions hurt the Libyan people's national income," Shakmak said. "Security is the basis of stability and is needed to ensure the presence of foreign companies here."
Separately, four security force members were injured during a failed attempt to evacuate protesters who have occupied the national assembly in Tripoli for weeks demanding compensation for injuries sustained in the 2011 war, the government said.
The group of about 30 war wounded have forced congress members to find temporary venues for sessions since last month.
When security forces tried to get them to leave on Sunday, the protesters fought back, throwing a grenade, officials said.