President Hassan Rohani says unrest that has left at least a dozen antigovernment protesters dead could be a chance to address problems plaguing Iran amid the biggest challenge to the authorities since violent demonstrations erupted after a disputed election handed Mahmud Ahmadinejad a second presidential term in 2009.
Speaking after a meeting with the heads of parliamentary committees, Rohani said the protests, which entered a fifth day on January 1, are not only about economic issues, but also a cry from citizens for more freedom.
The unrest "may seem to be a threat, but it can be turned into an opportunity to see what the problem is," the Fars news agency quoted Rohani as saying.
The unrest entered a fifth day on January 1, with demonstrations reported in several towns and cities, including Tehran where a car was set reportedly set alight.
Video posted on social media showed crowds of people -- some chanting "Death to the dictator!" -- walking through the streets of Tehran.
A police spokesman said on January 1 that one officer had been shot dead and three wounded during unrest in the city of Najaf Abad, the first reported security-force fatality since the antigovernment demonstrations began last week. It was unclear when the incident occurred.
The authorities have attempted to quell the uprising, which has been marked by crowds of hundreds of younger Iranians chanting antigovernment slogans and ripping up posters of Ayatollah Ali Khamenei, the Islamic republic's supreme leader, with strong warnings and by blocking popular social-media applications and disrupting some Internet services.
U.S. President Donald Trump said in a tweet that the upheaval shows Iran is "failing at every level" and that it was "TIME FOR CHANGE!"
"The great Iranian people have been repressed for many years. They are hungry for food & for freedom. Along with human rights, the wealth of Iran is being looted," he wrote.
The Russian Foreign Ministry said on January 1 that the unrest was "Iran's internal affair," adding that any "external interference destabilizing the situation is inadmissible." It did not elaborate.
German Foreign Minister Sigmar Gabriel expressed concern on January 1 about the death of protesters and urged the Iranian government to respect people's rights.
Israeli Prime Minister Benjamin Netanyahu praised the "brave Iranians" protesting against a regime that "wastes tens of billions of dollars spreading hate."
"I wish the Iranian people success in their noble quest for freedom," he said in a video posted on his Facebook page on January 1.
Iranian state TV reported on January 1 that at least 10 people were killed the previous night as demonstrations, sparked by rising costs of basic food supplies such as eggs and poultry, swept across the country.
The broadcaster gave no details on the most recent fatalities but said some armed protesters tried to take over some police stations and military bases but "faced serious resistance from security forces."
State TV's report would bring the number of dead to at least 12 after authorities confirmed two protesters were killed on December 30 in the western town of Doroud. In addition, hundreds have been arrested.
Actions on the streets of Tehran and other cities, including Sanandaj, Mashhad, Ilam, Khoramdareh, and Kermanshah, may have started over rising food prices, but demonstrators have also started to voice concerns over corruption allegations and government transparency.
Rohani, in his first public remarks since the start of the protests, said on December 31 that Iranians had the right to protest, but he warned that those demonstrations should not make the public "feel concerned about their lives and security."
WATCH: Rohani's address
That line appeared was backed up by judiciary chief Ayatollah Sadeq Amoli-Larijani, who called for a crackdown on "rioters" and "vandals."
"Those who have a demand must know that no one will get anywhere through disorder," he was quoted as saying by state TV Channel One on January 1.
Video and other information on social media showed protests taking place on December 31 in the capital, Tehran, and other cities, although crowd sizes were unclear.
Video footage appeared to show police in Tehran using water cannon to disperse demonstrators gathering in Ferdowsi Square in the center of the capital.
Officials said on December 31 that some 200 protesters in Tehran had been arrested the previous day.
Meanwhile, Iranian authorities have blocked popular social-media websites.
Users of the social networks Instagram and Telegram were unable to access the services on December 31.
Both applications are popular among Iranians and useful in helping set up gathering points for demonstrators who are disappointed with rising prices and Rohani’s unfulfilled promises to guarantee rights to freedom of expression and assembly.
The United States has condemned the arrest of protesters, with Trump cheering on the protesters via Twitter.
Trump tweeted on December 31 that it looks like the Iranians "will not take it any longer," adding, "The USA is watching very closely for human rights violations!"
Rohani criticized Trump over his tweets, saying he "has forgotten that he had called Iranian people 'terrorists' a few months ago."
Nikki Haley, the U.S. ambassador to the United Nations, also commented on the upheaval in Iran, saying Iran's government is "being tested by its own citizens."
"We pray that freedom and human rights will carry the day," she said in a statement on December 31.
Israel's intelligence minister voiced encouragement for the protests on January 1, but said his country's policy was not to get involved in Tehran's internal affairs.
Interior Minister Abdolreza Rahmani-Fazli warned earlier on December 31 that protesters who create unrest "are responsible for their actions and should pay the price."
The hard-line Revolutionary Guards and its Basij militia -- which led the crackdown against the 2009 protests -- have so far 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."