BENGHAZI, Libya (Reuters) - Libya's eastern Es Sider oil export port, the country's biggest, has been shut due to fighting nearby between forces representing the country's competing governments, an oil official said on Sunday.

Air strikes on Saturday by forces loyal to Libya's recognized government hit targets near the port, aiming to stop an advance by troops of the rival administration in Tripoli seeking to take control of oil facilities in the country's east.

Clashes were continuing near Es Sider, Tripoli-based al-Nabaa television station said on Sunday, adding that a force allied to the government in the capital was at the gates of the terminal.

The Ras Lanuf port east of Es Sider was still operating but the al-Waha Oil Co running the Es Sider port had halted work, the official said. A worker said staff had left the site for security reasons.

The company had been producing around 200,000 barrels a day, data from the state-run National Oil Corp (NOC) showed earlier this month. NOC had previously put the OPEC member's output at around 755,000 bpd, though this included some 140,000 bpd of refined products partly consumed locally.

Libya's oil industry had seen a modest recovery from a wave of protests until last month, when the 340,000 bpd-El Sharara oil field in the south closed due to clashes and a pipeline closure.

The fighting near the Es Sider port is part of a struggle in the North African country between competing governments allied to armed factions 3-1/2 years after the ouster of Muammar Gaddafi.

The recognized prime minister, Abdullah al-Thinni, has been forced into the east since a group called Libya Dawn seized Tripoli in August and set up its own government and parliament.

Ibrahim Jathran, head of a petroleum protection force guarding Es Sider and three other eastern oil ports, said his force had repulsed the advance.

"We confirm to the Libyan people that their resources are secure and under the protection of their sons," Jathran told a local television station. Appearing in military uniform, he said he remained loyal to Thinni and the House of Representatives, the assembly elected in June which also works out of the east.

Last month, Libya Dawn took control of El Sharara after a force allied to Thinni had withdrawn. But production remains shut down due to a pipeline closure by a rival group.

Jathran has threatened to call for eastern secession should world powers recognize the General National Congress, the rival assembly based in Tripoli.

(Reporting by Ulf Laessing and Ayman al-Warfalli; Editing by John Stonestreet and David Holmes)