US President Donald Trump said on Sunday that Iran's Kharg Island was being “blown to smithereens”, without providing details, as tensions between Washington and Tehran escalated after the first known US strikes on Iran in weeks.

Iran responded to an earlier US attack on rocket launchers on its island of Larak, about 660km east of Kharg, with an assault on two US bases in Jordan, Iranian media said.

The president’s post comes as the U.S. military carried out its first major attack against Iranian forces in the Strait of Hormuz this month.