The protest on Thursday night represented the first test of whether the Iranian public could be swayed by Crown Prince Reza Pahlavi, whose fatally ill father fled Iran just before the country's 1979 Islamic Revolution.
Demonstrations have included cries in support of the shah, something that could bring a death sentence in the past but now underlines the anger fuelling the protests that began over Iran's ailing economy.
The demonstrations that have popped up in cities and rural towns across Iran continued on Thursday. More markets and bazaars shut down in support of the protesters. So far, violence around the demonstrations has killed at least 42 people while more than 2270 others have been detained, said the US-based Human Rights Activists News Agency.
The growth of the protests increases the pressure on Iran's civilian government and its Supreme Leader Ayatollah Ali Khamenei. CloudFlare, an internet firm, and the advocacy group NetBlocks reported the internet outage, both attributing it to Iranian government interference.
Attempts to dial landlines and mobile phones from Dubai to Iran could not be connected. Such outages have in the past been followed by intense government crackdowns.
Meanwhile, the protests themselves have remained broadly leaderless. It remains unclear how Pahlavi's call will affect the demonstrations moving forward.
"The lack of a viable alternative has undermined past protests in Iran," wrote Nate Swanson of the Washington-based Atlantic Council, who studies Iran.
"There may be a thousand Iranian dissident activists who, given a chance, could emerge as respected statesmen, as labour leader Lech Wałęsa did in Poland at the end of the Cold War.
"But so far, the Iranian security apparatus has arrested, persecuted and exiled all of the country's potential transformational leaders."
Iranian officials have not acknowledged the scale of the overall protests, which raged across many locations on Thursday even before the 8pm demonstration. However, there has been reporting regarding security officials being hurt or killed.
The judiciary's Mizan news agency report a police colonel suffered fatal stab wounds in a town outside of Tehran, while the semiofficial Fars news agency said gunmen killed two security force members and wounded 30 others in a shooting in the city of Lordegan in Chaharmahal and Bakhtiari province.
A deputy governor in Iran's Khorasan Razavi province told Iranian state television that an attack at a police station killed five people on Wednesday night in Chenaran, some 700km northeast of Tehran. Late on Thursday, the Revolutionary Guard said two members of its forces were killed in Kermanshah.
Iran has faced rounds of nationwide protests in recent years. As sanctions tightened and Iran struggled after the 12-day war, its rial currency collapsed in December, reaching 1.4 million to $US1. Protests began soon after, with demonstrators chanting against Iran's theocracy.
It remains unclear why Iranian officials have yet to crack down harder on the demonstrators. Trump warned last week that if Tehran "violently kills peaceful protesters" America "will come to their rescue".
Speaking to talk show host Hugh Hewitt, Trump reiterated his pledge.
Iran has "been told very strongly, even more strongly than I'm speaking to you right now, that if they do that, they're going to have to pay hell", Trump said.
Trump demurred when asked if he'd meet with Pahlavi.
"I'm not sure that it would be appropriate at this point to do that as president," Trump said. "I think that we should let everybody go out there, and we see who emerges."
Meanwhile, Nobel Peace Prize laureate Narges Mohammadi remains imprisoned by authorities after her arrest in December.
with AP
