Palm Beach, Florida - President Donald Trump confirmed US forces were involved in "major combat operations" in Iran, vowing to overthrow the Islamic republic and "annihilate" targets.

In an eight-minute speech recorded at his Mar-a-Lago estate in Florida and posted on Truth Social, Trump announced the start of "massive and sustained operations" against Iran, not long after Israel announced it had launched its own strikes.

Running through a historically dubious timeline of conflict between Tehran and Washington, the 79-year-old again claimed Iran's leaders – whom he called "a vicious group of very hard, terrible people – had refused to abandon their pursuit of a nuclear weapons, despite their repeated and emphatic statements to the contrary.

Trump also complained about the country's ballistic missile program, which he said could in the future threaten the US "homeland," and promised to "annihilate" it.

The Republican called on Iranian armed forces and the powerful Islamic Revolutionary Guard Corps to unconditionally surrender and be granted "complete immunity" or face "certain death."

In a clear sign that a serious retaliation was expected, Trump acknowledged that "the lives of courageous American heroes may be lost and we may have casualties."

Finally, he encouraged the people of Iran to rise up and "take over your government."