Fresh U.S. military action against Iran and President Donald Trump’s declaration that the interim accord is effectively finished pushed oil prices higher while U.S. stock futures remained in positive territory.

Iran says it attacked sites linked to the US military in Kuwait, Bahrain and Qatar after US bombarded targets in Iran.

The United States launched a fresh wave of military strikes against Iran on Wednesday, targeting what it described as Tehran's ability to threaten shipping through the strategically vital Strait of Hormuz.

Trump had said that the ceasefire with Iran is "over" after Washington launched strikes on the country overnight, to which Iran responded by targeting US bases in the Gulf.

Trump ordered fresh strikes on Iran on July 8 and warned that the US would respond with much worse if Tehran continued attacking ships passing through the Strait of Hormuz, one of the world's busiest oil shipping routes.

President Donald Trump said the US would probably launch further strikes on Iran and could resume a blockade on the country’s ports, ratcheting up pressure on Tehran and raising the prospect of a return to all-out war.