RAS LANUF, Libya (Reuters) - Muammar Gaddafi loyalists killed 15 guards in an attack on an oil refinery on Monday in an apparent attempt to disrupt a drive by Libya's new rulers to seize the ousted leader's last bastions and revive the oil-based economy.
A Syrian-based television station said it would soon broadcast another message from the fugitive Gaddafi, who has issued regular battle calls to his followers in the three weeks since Tripoli was overrun.
The new ruling National Transitional Council (NTC) says that as long as Gaddafi remains on the run he is capable of attracting followers to a dangerous insurgency.
Witnesses to the refinery attack said the assailants damaged the front gate of the facility, 20 km (13 miles) from the coastal town of Ras Lanuf, but not the plant itself, which is not fully operational.
About 60 staff were there at the time of the attack, according to one of two wounded survivors at a hospital where the dead were also taken.
Refinery worker Ramadan Abdel Qader, who had been shot in the foot, told Reuters that gunmen in 14 or 15 trucks had come from the direction of the Gaddafi-held coastal city of Sirte.
"We heard firing and shelling at around 9 in the morning from Gaddafi loyalists," he said. Staff had been asleep.
The assault occurred only hours after the NTC announced it had resumed some oil production, which had been all but halted since anti-Gaddafi protests turned into civil war in March.
The interim council is struggling to assert its control over the entire country and capture a handful of stubbornly defended pro-Gaddafi towns.
Many senior NTC officials also see scooping up Gaddafi and the members of his family who are still on the run as crucial to finally declaring victory in the seven-month old war.
Gaddafi's son Saadi arrived in neighbouring Niger on Sunday after crossing the remote Sahara desert frontier. On Monday the U.S. State Department said that the government of Niger had confirmed to it that it intended to detain the former soccer player.
But a Nigerien government spokesman told Reuters that Saadi Gaddafi was only being watched for now.
"Nothing has changed in the government's position. There is no international search for him. Like the others he is just under surveillance," the spokesman said, referring to other Gaddadfi loyalists who have recently fled to Niger.
Two other sons and Gaddafi's only biological daughter have fled to Algeria. One son is reported to have died in the war and three others are still on the run.
The NTC has said it will send a delegation to Niger to seek the return of anyone wanted for crimes.
Niger, like Algeria, has cited humanitarian reasons for accepting fugitives of the former government, but has promised to respect its commitments to the International Criminal Court, which wants to try Gaddafi, son Saif al-Islam and intelligence chief Abdullah al-Senussi for war crimes.
NTC forces, which seized Tripoli on August 23, said they were meeting fierce resistance on the fourth day of fighting for the Gaddafi-held desert town of Bani Walid, 150 km (95 miles) southeast of the capital, and were edging towards Sirte.
Libya's economy is almost entirely dependent on oil, and restarting production is crucial to restoring the economy. Interim Prime Minister Mahmoud Jibril said on Sunday some oil production had resumed, but would not say where or how much.
Libya holds Africa's largest crude oil reserves and sold about 85 percent of its exports to Europe under Gaddafi. Western oil firms, including Italy's Eni and Austria's OMV, are keen to restore production.
Eni's chief executive told Reuters his priority was to restart gas exports via a pipeline from Libya to Italy by October or November. Resuming oil output was less urgent.
"We are by far the biggest player in Libya, both in oil and in gas, so I came here with the idea of 'back to normal'," Paolo Scaroni said during a visit to Tripoli.
In Bani Walid, fleeing residents reported intense street fighting while NATO warplanes could be heard overhead.
Families trapped there for weeks escaped after Gaddafi forces abandoned some checkpoints on the outskirts. Dozens of cars packed with civilians streamed out of the area.
"We are leaving because of the rockets. They are falling near civilian homes," said one resident, Ali Hussain.
The United Nations says it is worried about the fate of civilians trapped inside besieged pro-Gaddafi towns.
"Our big concern right now is Sirte, where we are receiving reports that there's no water and no electricity," U.N. humanitarian chief Valerie Amos told Reuters in Dubai.
The NTC has sent extra units to Bani Walid, but some fighters said this only worsened tribal tensions between fighters from other areas and those from the town.
"Our fighters are from all over Libya. There was little control over them yesterday. Today we will control them better," said NTC commander Mohamed el-Fassi.
He said five NTC fighters were killed and 14 wounded in Sunday's clashes.
Some NTC combatants said they suspected local fighters of the Warfalla tribe, Libya's largest, of passing tips to Gaddafi forces in Bani Walid. "We believe there are traitors among them," said Mohammed el Gahdi, from the coastal city of Khoms.
NTC military spokesman Ahmed Bani told reporters the plan for Bani Walid for now was to wait.
"When our forces entered Bani Walid they found the brigades of Gaddafi using citizens as shields," he said, adding that missile launchers had been placed on the roofs of homes, making it impossible for NTC forces or NATO warplanes to strike.
Additional reporting by Maria Golovnina north of Bani Walid, Emma Farge in Benghazi, William Maclean, Hisham el-Dani, Alexander Dziadosz and Mohammed Abbas in Tripoli, Mark John and Bate Felix in Niamey, Barry Malone and Sylvia Westall in Tunis, Keith Weir in London, Isabel Coles in Dubai and Andrew Quinn in Washington; Writing by Alistair Lyon and Barry Malone