WASHINGTON - The operator of a major US pipeline network shut down by a cyberattack said on Thursday it has resumed fuel deliveries, but gas stations up and down the east coast were still facing shortages after a wave of panic buying.

US President Joe Biden hailed the "good news" and urged the public to remain calm as supplies are restored over the next few days.

While "we'll not feel the effects at the pump immediately", there will be a "return to normalcy beginning this weekend and continuing in the next week", Biden told reporters at the White House.

Frantic motorists from Florida to Maryland had lined up at gas stations trying to fill their tanks and other containers, and the surge in demand sent the national average price above $3 a gallon (3.8 liters) for the first time since late 2014 despite government efforts to ease the supply crunch.

According to data on Thursday from the GasBuddy tracking site, about 70 percent of North Carolina's gas stations were still without fuel amid panic- buying and about half the stations in Virginia, South Carolina and Georgia were tapped out. Washington was among the hardest-hit locations, with 73 percent of stations out, the site's tracking service showed.

About a third of the stations in Florida, Maryland and Tennessee were out.

"I know seeing lines at the pumps or gas stations with no gas can be extremely stressful, but this is a temporary situation. Do not get more gas than you need," Biden said. "Don't panic."

Colonial Pipeline operates the largest fuel conduit system in the United States, which sends gasoline and jet fuel from the Gulf Coast of Texas to the populous east coast through 8,850 kilometers of ducts that serve 50 million consumers.

Colonial Pipeline shut down its network following a ransomware attack on its computer systems late on May 7.

Ransom paid?

According to a report by Bloomberg, the company paid a $5 million ransom to the hackers, contradicting a Washington Post report saying it would not pay to release its systems.

The governors of Virginia and North Carolina declared states of emergency to help ensure access to gasoline. Other governors urged people not to hoard supplies.

"There is available fuel supply in and around our state, and it will take time for tankers to move that supply to the stations that are experiencing shortages," North Carolina Governor Roy Cooper said. He reiterated calls for residents not to make any unnecessary trips to the pump, and at least five school systems in the state announced they would temporarily shift to remote learning due to the scarce fuel.