Iran's prosecutor general said on Wednesday that economic protests that had gripped the country were legitimate, but any attempt to create insecurity would be met with a "decisive response".
"Peaceful livelihood protests are part of social and understandable realities," Mohammad Movahedi-Azad told state media after three days of protests by shopkeepers in capital Tehran, which were joined by students across the country.
"Any attempt to turn economic protests into a tool of insecurity, destruction of public property, or implementation of externally designed scenarios will inevitably be met with a legal, proportionate and decisive response."
His comments came days after the Mossad intelligence agency of Iran's arch-foe Israel posted on social media that it was "with you on the ground" in a message to Iranian protesters.
Posting on its Persian-language X account, the spy agency encouraged Iranians to "go out into the streets together".
The spontaneous protests, driven by dissatisfaction at Iran's economic stagnation and galloping hyperinflation, began on Sunday in Tehran's largest mobile phone market where shopkeepers shuttered their businesses.
They have since built momentum, with students at 10 universities in the capital and in other cities, including Iran's most prestigious institutions, joining in on Tuesday.
Nevertheless, the protests remain limited in number and concentrated in central Tehran, with shops elsewhere in the sprawling metropolis of 10 million people unaffected.
Iran's economy has been in the doldrums for years, with heavy US and international sanctions over Tehran's nuclear program weighing heavily on it.
The currency, the rial, has also plunged in recent months, losing more than a third of its value against the US dollar since last year.
- Last-minute bank holiday -
The streets of Tehran were calm early on Wednesday, a change from the usual chaotic and choking traffic, with the authorities having announced a bank holiday with just a day's notice.
Schools, banks and public institutions have been closed with officials saying the directive was due to the cold weather and the need to save energy.
The capital's prestigious Beheshti and Allameh Tabataba'i universities announced that classes would be held online throughout next week for the same reason, the state-run IRNA news agency reported.
The authorities have not linked the bank holiday to the protests. Tehran is experiencing daytime temperatures in the low single digits, which is not unusual for the time of year.
Weekends in Iran begin on Thursdays, while this Saturday marks a long-standing national holiday.
Iran is no stranger to nationwide protests, but the latest demonstrations have not come close to the last major outbreak in 2022 triggered by the death in custody of Mahsa Amini, a young Iranian woman.
Her death in custody after being arrested for allegedly violating the strict dress code for women sparked a wave of anger across the country.
Several hundred people were killed, including dozens of members of the security forces.
