US President Donald Trump warned Iranian authorities against killing peaceful protesters, saying that Washington would “come to their aid.”
In a short post on social media, he wrote: “We are charged, loaded and ready to go.” He did not provide any additional details.
A senior adviser to Iran's Supreme Leader Ayatollah Ali Khamenei responded by saying Trump should “be careful” if he intervened, warning of potential chaos in the Middle East.
At least eight people have been reported killed in Iran after nearly a week of mass protests sparked by a worsening economic situation.
In a Friday post on Truth Social, Trump wrote: “If Iran shoots [sic] and brutally kill peaceful protesters, as is their custom, the United States of America will come to their aid.”
In his post, the US President did not specify what actions Washington might take against the Iranian authorities.
In June US strikes Iran's nuclear facilities on Trump's orders.
US officials later said the strikes had significantly set back Tehran's prospects of developing nuclear weapons – a claim that Iran disputes.
In retaliation, Iran launched a missile attack on a major US military base in Qatar.
Shortly after Trump's latest social media post, Khamenei adviser Ali Larijani issued his own warning.
“Trump must know that US intervention in this domestic issue will destabilize the entire region and destroy American interests,” he wrote.
In Iran, six people were reported killed on the fifth day of protests on Thursday.
Two people were killed in clashes between protesters and security forces in the southwestern city of Lordegan, according to the semi-official Fars news agency and rights group Hengaw.
Three people were killed in Aznay and another in Kukhdasht, all in the west of the country, Fars reported.
Fars did not specify whether those killed were protesters or security forces.
Hengau said the two killed in Lordegan were protesters, naming them Ahmad Jalil and Sajjad Valamanesh.
One death was reported in Fuladshahr in central Iraq and another casualty was reported in Marvdasht in southern Iraq.
The BBC was unable to independently confirm the death.
Footage posted on social media showed cars burning as clashes between protesters and security forces took place.
The BBC Persian Service verified footage of Thursday's protests in Lordegan, Tehran and Marvdasht.
Earlier, Iranian officials said a young member of the country's security forces was killed on Wednesday in the western city of Kukhdasht.
But protesters say the man was instead from their ranks and was shot dead by security forces.
On Friday, clashes were reported during the man's burial ceremony, which was attended by thousands of mourners. Uniformed security forces tried to carry his coffin, but the crowd snatched it from them and drove him away.
Protests began on Sunday in Tehran among shopkeepers angered by another sharp drop in the value of Iran's currency, the rial, against the US dollar on the open market.
By Tuesday, university students had taken part in the protest and it had spread to several cities, where people chanted against the country's clerical rulers.
Many protesters have since called for the end of Khamenei's rule. Some have said they want a return to the monarchy.
The protests were the largest since the 2022 uprising sparked by the death in custody of Mahsa Amini, a young woman accused by morality police of not wearing the veil properly, but they were not of the same scale.
President Masoud Pezeshkian said he would listen to the “legitimate demands” of protesters.
However, the country's attorney general, Mohammad Movahedi-Azad, warned that any attempt to create instability would be met with a “strong response.”
