US President Donald Trump has warned Iran's authorities against killing peaceful protesters, saying Washington will come to their rescue.

In a brief post on social media, he wrote: We are locked and loaded and ready to go, but provided no further details.

A senior adviser to Iran's Supreme Leader Ayatollah Ali Khamenei responded by advising Trump to be careful if he intervened, warning of potential chaos across the Middle East.

At least eight people are reported to have been killed in Iran after almost a week of mass protests sparked by worsening economic conditions.

In a post on Truth Social, Trump added: If Iran shots [sic] and violently kills peaceful protesters, which is their custom, the United States of America will come to their rescue. He did not specify what actions Washington could take against Iranian authorities.

In reaction to Trump's statements, Khamenei adviser Ali Larijani warned that US interference would destabilize the region and threaten America's interests.

Some protesters, however, welcomed the possibility of US intervention. A young woman participating in the protests expressed that US support has long been desired to counteract security force intimidation.

News reports confirm that the protests were sparked by shopkeepers in Tehran enraged by the sharp decline in the Iranian currency's value. University students quickly joined the demonstrations, which expanded across various cities with chants against the clerical regime.

"We don't have any kind of liberty here," declared one protester, emphasizing the brutal reality and the dire need for change in Iran, even at the cost of their lives.