Top exporter Saudi Arabia said it expected its oil facilities to escape unscathed from the gathering storm. Fellow Opec member the UAE also appeared to be outside the path of the storm, a shipping agent said.
Oman put its army and police on high alert, however, and warned the population of very high waves when winds of up to 205km per hour reached land.
In London, Brent North Sea crude for July delivery soared $1.33 to settle at $70.40 per barrel.
New York's main oil futures contract, light sweet crude for delivery in July, closed up a hefty $1.13 at $66.21 per barrel.
"Prices have turned around on news of a major tropical storm that has the potential to interrupt oil shipments from the Gulf," said Addison Armstrong of TFS Energy Futures in the US.
Oman produces just 715,000 barrels per day of oil, a small fraction of Saudi Arabia's almost 9 million bpd.
Earlier in the day, oil prices had drawn continued support from output disruptions in Nigeria that have tightened supplies of petrol-rich crude during peak summer demand.
Investors also took note of a defiant statement by Iran's Supreme Leader Ayatollah Ali Khamenei. He said Iran, the world's fourth biggest oil exporter, would not retreat from the "field of danger" to protect its right to develop nuclear technology.
In fellow Opec member Nigeria, militants have called a one-month truce in attacks on oil installations in the Niger Delta. But analysts saw little to suggest an end to 18 months of violence that has shut about a third of Nigeria's oil output.
"Nigeria is keeping the market quite tight," said Helen Henton, head of commodity research at Standard Chartered Bank.
She noted the International Energy Agency has called repeatedly for the Opec to increase production.
"But Opec is being quite strident about it being a US refinery problem," she said.
A series of outages at oil refineries in top oil consumer the US have contributed to a supply bottleneck in US petrol supplies, which are lower than usual.
Some refineries are now coming back onstream.
Oil had surged to a nine-month high above $71 on May 24, partly on concerns about Nigeria and US petrol prices.
Nigeria, 
OPEC, 
oil prices
UAE 
