Giant flames lit up the night sky in Tripoli.
After struggling to control the blaze at Libya’s largest fuel storage facility, shrapnel from rival militias fighting nearby struck a second tank and firefighters were forced to withdraw.
The national oil company now says the fire is out of control and could cause a humanitarian and environmental disaster, and evacuations have begun.
A call for international assistance remains unanswered as the country descends into chaos, with militia groups vying for power.
Western governments are closing embassies and pulling their nationals out, as battles between rival factions continue to rage at the main air terminal in the capital.
Reports overnight suggest at least 30 people have been killed in heavy fighting Benghazi involving warplanes and rockets.
“We have received 30 corpses so far,” a medical source said.
Two weeks of clashes has left around 160 people dead in Tripoli and eastern Benghazi.
Just three years on from the fall of Colonel Gaddafi, the government has warned of a possible break-up of the country if fighting continues.