An oil tanker laden with tonnes of petrol steamed into the port of Benghazi, with rebels on board claiming they seized the vessel from government control between Malta and Tripoli.
The 182-metre (600-foot) long "Cartagena" docked shortly before midday local time (1000 GMT), the lip of its black hull pressed toward the water line under the weight of what rebels said were 73,000 tonnes of gasoline.
A rebel soldier coming ashore said the vessel -- which was emblazoned with the initials of the state-owned General National Maritime Transport Company -- had been intercepted with the help of NATO two days ago "quite close to Tripoli."
"We had information about this boat with the help of NATO," said the rebel, who asked not to be named.
The fate of the crew was unclear, although the rebels said there was no resistance.
A NATO officer at the alliance's operational hub in Naples, Italy, said they had contact with the boat when it was hailed late on Wednesday afternoon.
Colonel Roland Lavoie told AFP that NATO officials had asked a series of specific questions of the ship's commander and had been satisfied enough to allow its continuation to Benghazi.
"We did not board this ship. We hailed it, and nothing was wrong according to us, so it was cleared to enter port," another official said.
With Libya's civil war approaching the sixth-month-mark fuel reserves have been run down on both sides of the front line.
In the rebel-held east, petrol shortages are uncommon, but the rebels' National Transitional Council has struggled to pay for all of the fuel needed to run power stations, water plants and other utilities.
But the loss of the cargo will be a blow to Tripoli, where citizens have been suffering crippling fuel shortages as a result of fighting and international sanctions.
The Cartagena docked close to another tanker, the Anwar Afriqya, which was seized in March.
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