The Brent crude oil benchmark went above $US115 a barrel during Thursday trading in Asia, more than five per cent higher than Tuesday's prices.
US West Texas Intermediate crude rose 57 cents, or 0.6 per cent, to $US96.89 a barrel, after earlier gaining almost $US4 to trade at $US100.02.
WTI has been trading at its widest discount to Brent in 11 years due to releases from US strategic reserves and higher freight costs, while renewed attacks on Middle Eastern energy facilities boosted support for Brent.
"Escalation in the Middle East, precise attacks on oil infrastructure, and the death of Iranian leadership all point to a prolonged disruption in oil supplies," Phillip Nova analyst Priyanka Sachdeva said in a note.
"Adding fuel to the fire, the Federal Reserve served 'steady rates' with a hawkish narrative, pointing to the economic concerns that follow a war."
The US central bank held interest rates steady on Wednesday, projecting higher inflation as policymakers take stock of the impact of the US-Israel war with Iran.
On Wednesday, QatarEnergy said Iranian missile attacks on Ras Laffan, the site of Qatar's core LNG processing operations, caused "extensive damage" to its energy hub.
Saudi Arabia said it intercepted and destroyed four ballistic missiles launched on Wednesday toward Riyadh and an attempted drone attack on a gas facility.
Saudi Aramco's SAMREF refinery in the Red Sea port of Yanbu was also targeted in an aerial attack on Thursday. Kuwait Petroleum Corporation said an operational unit at its Mina al-Ahmadi refinery was hit by a drone, igniting a limited fire.
Iran issued evacuation warnings before its attacks for several oil facilities across Saudi Arabia, the UAE and Qatar, as it prepared to retaliate for strikes on its own energy infrastructure in South Pars and Asaluyeh.
South Pars is the Iranian sector of the world's largest natural gas deposit, which Iran shares with US ally Qatar on the other side of the Gulf. Israel carried out the South Pars gas field attack, but the United States and Qatar were not involved, President Donald Trump said.
