By Bo Erickson and Enas Alashray, Reuters

The United States began a fresh round of strikes against multiple targets overnight (local time) in Iran, the US military said, hours after President Donald Trump vowed new attacks if no peace deal is secured.

"The strikes are in response to Iran's unwarranted and continued aggression," the military's Central Command said in a post on X, adding that the strikes began at 5.15pm EDT (9.15am NZT), which was 12.45am in Tehran.

The attacks are the latest development in an escalating exchange of strikes that threaten to reignite a full-scale war, which was paused in early April when the two sides agreed to a fragile ceasefire.

An explosion was heard in the port city of Sirik, and air defenses were activated in west Tehran, Iran's Mehr news agency reported.