US President Donald Trump on Sunday warned Iran it would get "hit very hard" if more protesters die during the unrest that has rocked the country over the past week.
"We're watching it very closely. If they start killing people like they have in the past, I think they're going to get hit very hard by the United States," Trump told reporters aboard Air Force One.
He did not elaborate as to what steps the US might be considering.
At least 19 protesters have been killed during the unrest, the organization Iran Human Rights, which is based in Oslo, reported on Sunday. Hundreds more are said to have been injured and arrested, the organization said.
The Iranian government continues to provide no information about the unrest and casualties. Current figures rely mainly on reports from social media and activists abroad. These reports cannot be independently verified.
Initially, people protested only in Tehran against the government's economic policy, but soon it developed into nationwide political unrest. In addition to the criticism of the leadership, there are also calls for a return of the monarchy, which was overthrown by the Islamic Revolution in 1979.
On Friday, Trump pledged his support to those taking part in the protests in a post on Truth Social.
"If Iran shots [sic] and violently kills peaceful protesters, which is their custom, the United States of America will come to their rescue," he wrote.
"We are locked and loaded and ready to go."
The US and Iran have been arch enemies since the Islamic Revolution and have no formal diplomatic relations.
In June, the US military joined Israel's war against Iran and bombed key nuclear facilities there. The US and Israel accuse Iran of wanting to build a nuclear bomb, a charge that Tehran denies.
