* Marsa Al Hariga port opens for oil exports
* Es Sider, Ras Lanuf, Zueitina still shut
* PFG defuses protest, fires rogue Es Sider leader
* Mystery ship A Whale at Es Sider baffles port, officials (Adds detail, context)
By Feras Bosalum and Julia Payne
TRIPOLI/LONDON, Aug 19 Libya's largest crude oil export terminals were still shut on Monday but the reopening of a smaller one could pave the way to a wider solution to the worst disruption to the country's oil industry since the civil war.
The Marsa al Hariga port resumed full operations and is ready to export following worker strikes, an oil ministry spokesman said.
It was not immediately possible to reach Arabian Gulf Oil Co who participated in closing the oilfields, which feed the port and the country's largest refinery.
But there was scepticism in the market given false restarts last week at other ports.
"We need to see a vessel berth and load," one trader said, who has a tanker waiting nearby.
Pay strikes and other protests at Libya's two largest ports as well as oilfields have pushed crude oil output and exports to the lowest levels since the civil war that ousted Muammar Gaddafi in 2011.
About half of the country's over 1.2 million barrel per day export capacity was still shut down, a variety of sources said, including the largest Es Sider terminal.
The crisis hit a peak at the end of last week when the government threatened military action should the striking security guards at Es Sider sell oil independently.
But the striking guards are under mounting pressure from colleagues at other local ports, several Libyan sources said, and have seemingly failed to build wider momentum to sell oil independently.
While the chairman of the Petroleum Facilities Guard (PFG), of which many are striking, has taking the lead in negotiating settlements. Though it will be a test to see if they are lasting.
"(Edris) succeeded to defuse the strike at Tobruk and Marsa al Hariga and now he's working on Zueitina," one senior Libyan oil official told Reuters.
Edris Abokhamada became head of the PFG at the start of August, replacing Rasheed Al Sabri.
The loyalty of the PFG heads and some disunity among oil workers in the east is leaving the leader of the Es Sider and Ras Lanuf protest somewhat isolated.
"We received a letter from employees at the Brega port saying they are against the port closures and will work under the government," a PFG spokesman said.
"Ibrahim has been removed from his position by the chief of staff," the spokesman added, and he expected the other ports to reopen soon.
The government said last week that Ibrahim al-Jathran, head of the middle region for the PFG, was seeking to sell oil for the benefit of his group of strking oil workers.
The senior Libyan official said al-Jathran was seeking fame by changing sides and added that he knows nothing about the oil business.
The PFG operates under the Defence Ministry to protect oil installations, but only about 2,000 of its 15,000 members have had training from the military.
ES SIDER MYSTERY
Libya's still shut Es Sider has around eight crude oil tankers at waiting to load at anchor. However, there were concrete signs some oil deal, independent of state National Oil Corp, might be under way.
Trading sources and employees at Es Sider said there was one mysterious tanker waiting outside that was unaccounted for and market sources did not know who had chartered it.
"We are calling the tanker, but we are not able to reach the captain," one of the port workers said.
A Libyan Coast Guard vessel, the Toukra Tess, entered the port of Es Sider on Saturday, maritime analytics firm WindWard said. (Additional reporting by Ron Bousso; editing by William Hardy)