Most of the crowd worked for Waha Oil, a joint venture with American firms ConocoPhillips, Marathon and Amerada Hess .

Documents proving managers had used the Waha Oil complex as a base for Qaddafi fighters had been presented to the NOC chairman that morning, protesters said.

The oil fields had been targeted by NATO because they were used to feed, shelter and equip loyalist fighters, according to the workers, who said it could take four to six months to restart flows.

“There is a lot of damage at the fields ... especially at Gialo and Waha,” said Ahmed Zahmun, a Waha Oil protester.

In a recent interview, the NOC’s chairman said NATO airstrikes on Libyan oil fields had been executed with “surgical precision.”

A source at NOC confirmed Nouri Berouin, the chairman, had met Waha Oil workers on Sunday, but added requests to remove directors had not been heeded.

Other North American firms in Libya are facing contrasting fortunes, with Occidental and Suncor both restarting production at fields in the eastern part of the Sirte basin this week.

European companies, including German, Italian and French oil firms, have also succeeded in pumping oil for the first time since war broke out, but they have met with mixed fates as well.

An operations manager at Eni’s headquarters in Tripoli said recently that the Italian oil and gas company’s largest oilfield, Elephant, lay in ruins and would not restart until 2012. Eni’s CEO later said the company did not know of any damage to the field.

So far, oil has yet to flow from the West and parts of Libya’s oil-rich basin remain too dangerous to inspect.

Waha Oil pumped just under 400,000 barrels of oil per day (bpd) before the war, but is now producing no crude and field workers say they will not return until managers were replaced.

Protesters said Libyans had been denied the opportunity to get a good job throughout Qaddafi’s rule and wanted a better future.

“After more than 40 years, we are still relying on foreign workers. Libyans have no chance to get a good position. Nothing has changed. There is no future strategy,” said Ahmed Zahmoul.

Berouin has said the OPEC member’s current production stands at about 25 percent of its prewar levels and full output could come in about 15 months.

Chairman Berouin also said Libya is currently producing about 390,000 barrels per day and he was optimistic that prewar production levels of about 1.6 million barrels per day could come in 14 to 15 months.

He said the interim government would honor existing contracts, but it was up to the next government to decide on new licensing rounds or agreements.

Sunday’s protest followed a similar demonstration at Waha Oil’s headquarters recently. Engineers there reported damage was severe in parts of the complex, while some oil fields were still unsafe to visit.

Waha Oil workers were joined by employees at the Libyan Petroleum Institute, who also said their managers had actively supported Qaddafi’s army.

“They stored TNT in the building. The army came there for rifles and machine guns,” said Ibrahim Twebti, an employee at the institute.

Punishment was up to the Libyan court charged with processing Qaddafi loyalists, protesters said, but whatever the result, managers were unqualified for their jobs and should not be allowed to stay on.

“They were endorsed by Qaddafi. Positions were seen as property. We want to change that,” said Hatem Wafa, a geophysicist at the protest.