"If Iran shoots and kills peaceful protesters, as is their custom, the United States will come to their rescue," Trump wrote on his Truth Social platform, adding that he was "ready."
Ali Larijani, spokesman for Iran's National Security Council, responded on X and accused the US and Israel of being behind the protests.
On Sunday, shopkeepers in Tehran took to the streets to protest skyrocketing costs and declining living standards. The protests have since spread, with violent clashes reported from several parts of the country.
The state-run Fars news agency reported that several people had been killed. Separately, 30 people were arrested in Tehran, accused of "disturbing public order," the state-affiliated Tasnim news agency reported.
