* Reuters correspondent sees sustained rebel fire on base
* Army fires back
(Updates with detail from the battlefield)
NEAR RAS LANUF, Libya, March 4 (Reuters) - Anti-Gaddafi rebels fired a sustained barrage of mortar bombs and rockets at a military base in the oil terminal of the eastern port of Ras Lanuf on Friday and the army returned fire with artillery.
"There are lots of flames, thuds and bangs. There is the wailing of sirens and puffs of smoke in the air," said Reuters correspondent Mohammed Abbas who could see the battlefield.
"More and more rebels with heavy artillery are streaming by to the front-line," said Abbas, adding "an anti-aircraft gun mounted on a truck and an anti-tank gun were the latest to go by". It was not clear if there had been any casualties in the exchange of fire.
The rebel forces, who were about 10 kms (six miles) from Ras Lanuf, had been firing for about one hour towards the base and the army had been defending the position.
Rebels were firing their assault rifles at helicopters overhead which fired machine guns at the rebel positions. A helicopter fired a missile which failed to explode.
The rebels had said they were determined to over-run the military base on the outskirts of Ras Lanuf, a major oil port on the Mediterranean Sea, which has a refinery, pipelines, a terminal and which is 660 km (410 miles) east of Tripoli. (Reporting by Mohammed Abbas; Writing by Tom Perry and Peter Millership in Cairo; Editing by Jon Boyle)