The assault came hours after the rebels exported their first cargo of oil into the international market, potentially opening the door to millions of dollars of funding to sustain their uprising against Colonel Gaddafi’s 41-year rule. The attack against oilfields in the east was the first against production facilities. Previously, only port facilities and crude oil storage tanks in the Es Sider and Ras Lanuf, also in the east, were damaged during the conflict.

While storage could be repaired relatively quickly, production facilities are far more complex, particularly if oil wells caught fire.

Abdul Jalil Mayuf, an official at the Arabian Gulf Oil Company, said production had been stopped “because it was not safe” following an attack on the Misla field by pro-Gaddafi troops. “It’s not safe in the fields,” he said.

The attacks on the fields came as Arab nations backing the use of force in Libya were being urged to help train and guide rebel fighters as western military planners prepare for involving ground forces.

Amid fears of a prolonged stalemate, the UK and France are approaching Qatar and the United Arab Emirates to provide or fund military specialists to bring some fighting discipline to a ragtag opposition force.

This guidance, which could be supplied by military contractors, would be modelled loosely on the clandestine ground support and air cover provided for the irregular Northern Alliance fighting the Taliban in Afghanistan in 2001.

Air strikes halted forces loyal to Col Gaddafi from advancing on Benghazi but the planners realise it will take more than that to tip the balance.

Nato members are unwilling to provide troops to train or co-ordinate the rebels, leaving a question mark over how the next phase of the conflict can be prosecuted to give the opposition the upper hand.