The price for a barrel of Brent crude, the international standard, was at $US101.19 ($A144.78) shortly after trading resumed on the Chicago Mercantile Exchange on Monday, up 9.2 per cent from its settlement price of $US92.69 ($A132.62) on Friday.
West Texas Intermediate, the light, sweet crude oil produced in the United States, was selling for about $US107.06 ($A153.18) a barrel.
That's 16.2 per cent higher than its Friday settlement price of $US90.90 ($A130.06).
Both could rise or fall as market trading continues.
The increases followed US crude prices jumping by 36 per cent and Brent crude prices rising 28 per cent last week.
Oil prices have surged as the war, now in its second week, ensnared countries and places that are critical to the production and movement of oil and gas from the Persian Gulf.
Roughly 15 million barrels of crude oil - about 20 per cent of the world's oil - typically are shipped every day through the Strait of Hormuz, according to independent research firm Rystad Energy.
The threat of Iranian missile and drone attacks has all but stopped tankers from travelling through the strait, which is bordered in the north by Iran, carry oil and gas from Saudi Arabia, Kuwait, Iraq, Qatar, Bahrain, the United Arab Emirates and Iran.
Iraq, Kuwait and the UAE have cut their oil production as storage tanks fill due to the reduced ability to export crude. Iran, Israel and the United States also have attacked oil and gas facilities since the war started, exacerbating supply concerns.
The last time US crude futures traded above $US100 ($A143) per barrel was June 30, 2022, when the price reached $US105.76 ($A151.32). For Brent, it was July 29, 2022, when the price hit $US104 ($A149) per barrel.
The global surge in oil prices since Israel and the US attacked Iran on March 1 has rattled financial markets, sparking worries that higher energy costs will fuel inflation and lead to less spending by US consumers, the main engine of the economy.
In the US, a gallon of regular gasoline rose to $US3.45 ($A4.94) on Sunday, about 47 cents more than a week earlier, according to AAA motor club. Diesel was selling for about $US4.60 ($A6.58) a gallon, a weekly increase of about 83 cents.
The price of natural gas has also climbed, though not as much as oil. It rose about 11 per cent last week and ended Friday at $US3.19 ($A4.56) per 1,000 cubic feet.
If oil prices stay above $US100 ($A143) per barrel, some analysts and investors say it could be too much for the global economy to withstand.
Over the weekend, Israel's military struck oil depots in Tehran and four oil storage tankers and a petroleum transfer terminal.
Mohammad Bagher Qalibaf, the speaker of Iran's parliament, said the war's impact on the oil industry would spiral, warning it soon could become harder to produce and sell oil.
Iran exports roughly 1.6 million barrels of oil a day, mostly to China, which may need to look elsewhere for supply if Iran's exports are disrupted, another factor that could increase energy prices.
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