Iran's interior minister warned on December 31 that "violence, fear and terror" will be confronted after three days of protests against the establishment.
"Those who damage public property, disrupt the order and break the law must be responsible for their behaviour and pay the price," Abdolrahman Rahmani Fazli said on state television.
"The spreading of violence, fear and terror will definitely be confronted. The vigilance and intelligence of people has always led any plot to fail," he said.
A video from the third day of anti-government protests in Iran appears to show clashes outside a Revolutionary Guards base in Bandar Abbas:
Iran's Street Protests Turn Deadly, As Government Warns of 'Iron Fist' Response
By RFE/RL's Radio Farda
At least two protestors were killed in antigovernment street protests in Iran, as demonstrations originally prompted by anger over rising prices intensified and spread to the capital, Tehran, prompting government warnings of an “iron fist” response.
The demonstrations, with increasing violence in their third day on December 30, are the largest and the most serious challenge to the authorities since 2009 following the disputed presidential election of then-President Mahmud Ahmadinejad.
The semiofficial news agency Mehr quoted Habibollah Khojastepour, deputy governor of Lorestan Province, as saying on December 31 that an illegal gathering in the western town of Doroud ignited clashes where "two of our dear Doroudi citizens were killed."
"No shots were fired by the police and security forces. We have found evidence of enemies of the revolution, Takfiri groups, and foreign agents in this clash," he added later on state television. Takfiri is a term used for Sunni militants, especially the Islamic State.
However, a video posted on social media purported to show two young men after they were shot dead by riot police.
RFE/RL could not verify the authenticity of the video, but the Voice of America identified the victims as Hamzeh Lashni and Hossein Reshno. VOA said a reporter with its Persian service had spoken to their families.
The video showed a protester chanting, "I will kill whoever killed my brother!"
Brigadier-General Esmail Kowsari, deputy security chief in Tehran for the Islamic Revolutionary Guards Corps, was quoted by the ISNA news agency as saying on December 30 that while the situation in the capital was under control, protesters would face "the nation's iron fist" if they continued.
"If people came into the streets over high prices, they should not have chanted those [antigovernment] slogans and burned public property and cars," Kowsari said.
The violence comes as separate state-sponsored rallies took place around the country to mark the end of the unrest that shook the country in 2009. State television reported pro-government rallies were held in some 1,200 cities and towns.
The antigovernment protests were sparked by a surge in prices of basic food supplies, such as eggs and poultry.
They quickly spread to many cities where hundreds of protesters have been chanting slogans against the Islamic establishment and the country’s Supreme Leader Ayatollah Ali Khamenei.
Some have also chanted slogans against Iran’s foreign policies, including its support for the regime of Syrian President Bashar al-Assad.
Social media postings said protests broke out on December 30 in cities including Tehran, Shahr-e Kord, Kermanshah, and Zanjan.
Reports said that in some cities protesters set government buildings and police vehicles on fire.
Social media video from the city of Mashhad showed protesters overturning a police car and setting police motorcycles on fire.
The semiofficial Mehr news agency posted videos of protesters attacking a town hall in central Tehran, overturning a police car, and burning the Iranian flag.
Amateur videos posted online appeared to show clashes at Tehran University, where police forces reportedly used tear gas to disperse protesters.
“Seyed Ali [Khamenei] Shame On you. Leave The Country Alone,” protesters chanted at the university according to a video sent to RFE/RL's Radio Farda from the Iranian capital.
In another video from Tehran, protesters appear to tear down a Khamenei poster.
'Internet Distuptions'
The protests took place amid reports of Internet disruptions, with the New York-based Center for Human Rights In Iran saying the government was making it difficult for Iranians to get online.
“This means that the vast majority of Iranians cannot access mobile apps or websites or anything that has its servers outside Iran without very robust circumvention tools,” the group said on Twitter.
Iran has slowed in the Internet during past protests in order to prevent the spread of information, and Interior Minister Abdolreza Rahmani-Fazli warned against promoting protests online.
"We ask people not to take part in unlawful gatherings, if they plan a gathering they should apply ([or a permit], and it will be examined," Rahmani-Fazli told the Young Journalists Club news website.
The hard-line Revolutionary Guards and its Basij militia -- which led the crackdown against the 2009 protests -- so far had appeared to stay away from the demonstrations. However, in a statement carried by state media, it said, "The Iranian nation...will not allow the country to be hurt."
“This is more grass-roots. It’s much more spontaneous, which makes it more unpredictable,” Alex Vatanka, an Iran expert at the Middle East Institute in Washington, told The Washington Post.
“Things are not working out economically for ordinary Iranians,” he added. “But the root causes, and the much deeper resentment, go back decades. People do not feel this regime represents them.”
WATCH: Iranians In Eastern Cities Protest Over Economic Troubles (from December 28)
Dozen have been arrested during the three days of protests.
Trump: 'The World Is Watching'
The United States condemned the arrests, with President Donald Trump warning Tehran in a tweet that "the world is watching."
"Many reports of peaceful protests by Iranian citizens fed up with regime’s corruption & its squandering of the nation's wealth to fund terrorism abroad," Trump wrote on Twitter, echoing an earlier White House statement.
"Oppressive regimes cannot endure forever, and the day will come when the Iranian people will face a choice. The world is watching!" Trump added in a tweet.
U.S. Senator John McCain later said in a tweet that “for too long, the Iranian people have been oppressed by their government, which cares more about sowing instability abroad than its own citizens.”
Iran's Foreign Ministry spokesman, Bahram Ghasemi, was quoted on state TV on December 30 as saying that the "Iranian people give no credit to the deceitful and opportunist remarks of U.S. officials or Mr. Trump."
Massoumeh Ebtekar, vice president in charge of women's affairs, wrote on Twitter: "Although people have a right to protest, protesters must know how they are being directed."
She posted images from Twitter accounts based in the United States and Saudi Arabia, voicing support for the Mashhad protests.
With reporting by The Guardian, VOA, Reuters, AFP, AP, and dpa