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US motorists have been urged not to hoard fuel as a major US fuel pipeline remained shut down after a cyber-attack.
Petrol stations from Florida to Virginia began running dry and pump prices rose.
The average price for petrol stood at $2.98 (£2.11) per gallon on Tuesday, its highest since November 2014, the American Automobile Association said.
Some motorists in the south east were pictured stocking up on fuel.
But US Energy Secretary Jennifer Granholm said there was no need for motorists to hoard petrol.
Ms Granholm said there was not a shortage but a supply "crunch" in North Carolina, South Carolina, Tennessee, Georgia and southern Virginia, regions that typically rely on Colonial for fuel.
A ransomware cyber-attack on Friday forced Colonial Pipeline to shut down the main part of its network.
The operator has forecast that it will not substantially restore operations of the 5,500-mile (8,900km) pipeline network that supplies nearly half of the East Coast's fuel until the end of the week.
The gang is believed to be based in Russia or Eastern Europe and avoids targeting computers that use languages from former Soviet republics, cyber experts said.
Ransomware is a type of malware designed to lock computers by encrypting data and demanding payment to regain access.
Russia's embassy in the US rejected speculation that the country's government was behind the attack.
President Joe Biden a day earlier said there was no evidence so far that Russia was responsible.
More than 7% of petrol stations in Virginia and 5% in North Carolina had no fuel on Tuesday as demand jumped 20%, tracking firm GasBuddy said.
On Tuesday, the government stepped in to issue an emergency fuel waiver lasting one week, designed to help alleviate any shortages.
The Environmental Protection Agency (EPA) said the move, which relaxes some rules usually applied to fuel, would run until 18 May in Pennsylvania, Virginia, Maryland, and Washington DC.
In addition, Georgia suspended sales tax on petrol until Saturday.
On Monday North Carolina declared a state of emergency and temporarily suspended vehicle fuel regulations "to ensure adequate fuel supply supplies throughout the state".
While the pipeline outage is having short-term consequences in some regions, some experts believe the longer term impact will be small.
"Markets will go crazy, but two weeks later no one knows it happened," said Chuck Watson, director of research at Enki, which studies the economic effects of natural and other disasters.
Fuel prices were expected to rise with the start of the summer driving season, although the US Energy Information Administration said on Tuesday that the ongoing effects of the Covid-19 pandemic would "significantly affect petroleum markets in the summer of 2021".
The pipeline shutdown contributed to the rise in fuel prices, the AAA said.
"We might see the delivery challenges due to the attack add a few cents to the expected increase in the national average," a spokesperson added.