BENGHAZI, Libya (Reuters) - A rocket hit a tank at the eastern Libyan oil port Es Sider as armed factions allied to competing governments fought over control of the country's biggest export terminal, officials said on Thursday.

Es Sider and its adjacent Ras Lanuf terminal have been closed since a force allied to a rival government in Tripoli moved east trying to take them.

"A tank was hit but the damage is limited," said an official from a security service allied to the internationally-recognised government, now operating from eastern Libya. He said there were heavy clashes in the Ben Jawad area west of Es Sider where he said some of the rival forces were based.

An oil ministry official said the tank was still on fire. Smoke could be seen on pictures posted on social media websites and described as showing the port. No more information was immediately available.

The fighting had reduced Libya's crude output to 352,000 barrels a day, a spokesman for state-owned National Oil Corp (NOC) said. Only the Brega, Sarir, Messla and offshore operations were still producing, he said.

Libya has had two governments and parliaments since a group called Libya Dawn seized the capital Tripoli in August by expelling a rival faction, installing its own prime minister and forcing the internationally-recognised cabinet to operate out of the east with the elected House of Representatives.