Donald Trump has flagged the US could hit Iran "hard" with fresh strikes in coming hours after declaring the ceasefire between the two countries is at an end after reported attacks on vessels in the Strait of Hormuz.

Both the US and Iran said they had hit dozens of targets, placing fresh strain on their interim deal to end the war.

Washington launched strikes on the Islamic Republic overnight in response to ships being hit in the Strait of Hormuz. Iran retaliated by targeting US bases in the Gulf.