Forces loyal to Muammar Gaddafi and rebels fought for control of the oil town of Brega on Tuesday as the battle for eastern Libya edged closer to the insurgent stronghold Benghazi, rebel fighters said.

Al Jazeera television reported that army units commanded by Gaddafi's sons were heading towards Brega, suggesting the Libyan leader was moving some of his best troops to the rebel-held east.

The channel said the units were commanded by his sons Saadi and Khamis.

Government warplanes also strafed rebel forces at Ajdabiyah, about 75 km (50 miles) from Brega on the coastal highway and the gateway to the major eastern city of Tobruk.

"In Brega it is still advance and retreat, we are not in control and they are not either," fighter Hussein al-Wami told Reuters on Tuesday morning.

His report was seconded by fighter Addel Ibriki, who had just returned to Ajdabiyah from Brega.

"It is still to and fro," Ibriki said.

However, the head of the oil workers' union said in Tripoli that all Libya's oil export terminals except Tobruk were back in government hands. Brega has an oil terminal.

"All of the terminals are under control, except Tobruk," said union chief Mohammed Abu Sittah.

Claims of defeats and victory have been difficult to verify immediately and towns have changed hands several times in the past.

Gaddafi's forces have advanced steadily eastwards along the coast to retake towns captured by rebels in the early days of the insurrection against his 41-year-rule.

The poorly-equipped rebels have been outgunned by Gaddafi's tanks, artillery and warplanes and are in danger of being pushed back to Benghazi, headquarters of their provisional national council.

The movement of units commanded by Gaddafi's sons indicated a new resolve to crush the rebels swiftly and emphatically.

In western towns, residents had said units of the 32nd Brigade have been used to quell the revolt. This unit is commanded by Khamis and, according to military analysts, is the best-trained and equipped force available to the Libyan leader.

When violence engulfed Benghazi in mid-February, Saadi spoke on local radio to say he had been appointed commandant of the city. Soon after, residents took control of Benghazi and forced out Gaddafi's forces.

WATCHING PLANES

Two government warplanes flew over Ajdabiyah on Tuesday, with one of them firing two rockets, rebel fighters said.

"There has just been an air strike. There were two planes, only one fired, it was close to the western gate," fighter Ahmed Miftah said.

At the gate and throughout the rebel-held town, people watched a plane circling overhead, asking if it was a warplane or a civilian aircraft.

"Don't be stupid these are not civilian planes flying," one man said.

Thuds and bangs could be heard in the distant but it was unclear if it was the sound of an attack or rebels firing from their positions.

Ajdabiyah has been on edge since Gaddafi's forces began bombing and shelling it on Sunday. The town is a gateway to regions further east and a 400 km (250 mile) desert road offers a clear route straight to Tobruk, near the Egyptian border.

Libyan state television has carried messages saying eastern towns and cities would be or had been "liberated" from the hands of what it calls "armed gangs" and terrorists inspired by al Qaeda. Since halting the rebel advance, Gaddafi's forces have recaptured the oil towns of Es Sider and Ras Lanuf.