US President Donald Trump has warned Iranian authorities against violence against angry protesters, saying "oppressive regimes cannot endure forever."
Trump wrote on twitter, "The entire world understands that the good people of Iran want change" and touted that other than US military might, its people's will is what leaders in Iran feared the most.
he also wrote that "the world was watching" millions of Iranians getting bored with the corruption under clerical rule and wasting the country's cash to support terrorism all over the world.
The US State Department condemned the arrests and urged "all nations to publicly support the Iranian people and their demands for basic rights and an end to corruption".
Iranian major cities are now being hit by sweeping anti-government protests.
The protests that erupted Thursday saw millions of Iranians in cities of Rasht, Kermanshah, Isfahan, Hamadan and elsewhere opposing economic problems and clerical rule in the Shiite country.
Reacting to the protests that spread now to the capital Tehran, the security forces arrested dozens of demonstrators and blocked the main bridges.
In a secret meeting with commanders of Iranian Revolutionary Guard Corps (IRGC), Khamenei ordered the arrest of several politicians who support the protests including the former President Mahmoud Ahmadinejad.