Israel kept up intense pressure on Lebanon with strikes it said targeted Iran-backed Hezbollah militants, hitting multiple apartment buildings in Beirut and killing at least six people.

In Iran, the Bushehr nuclear power plant complex was hit by a projectile but there were no injuries and the plant suffered no damage, the International Atomic Energy Agency said after receiving a report from Tehran.

The IAEA's leader, Rafael Grossi, reiterated his call "for maximum restraint during the conflict to prevent risk of a nuclear accident."

The price of Brent crude oil, the international standard, remained stubbornly over USD 100 per barrel in early trading on Wednesday, up more than 40 per cent from the start of the war.

Since the United States and Israel attacked Iran to start the war on February 28, Iran has been targeting the energy infrastructure of its Gulf Arab neighbours, as well as military bases, as part of a strategy to drive up oil prices and put pressure on Washington to back down.