The Iranian army says it will defend the country’s “national interests” as antigovernment protests continue to escalate amid widespread arrests and an internet blackout.

In a statement published by semi-official news sites on Saturday, the military accused Israel and “hostile terrorist groups” of seeking to “undermine the country’s public security”.

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“The Army, under the command of the Supreme Commander-in-Chief, together with other armed forces, in addition to monitoring enemy movements in the region, will resolutely protect and safeguard national interests, the country’s strategic infrastructure, and public property,” it said.

The warning came as Tehran has stepped up efforts to ‍quell the country’s largest protests in years, which have seen thousands of people take to the streets in anger over the soaring cost of living and inflation.

Crowds gathered again on Saturday in the north of the Iranian capital, Tehran, setting off fireworks and banging pots as they shouted slogans in support of the country’s ousted monarchy, according to video verified by the AFP news agency.

Other videos that could not be immediately verified also showed rallies in the city of Rasht in the north, Tabriz in the northwest, and Shiraz and Kerman in the south.

Demonstrations have taken place across Iran since late December, with growing calls for the end of the clerical system that has governed the country since the 1979 Islamic revolution.

Human rights groups have urged restraint amid reports of protest-related casualties and mass arrests, with Norway-based NGO Iran Human Rights saying at least 51 protesters, including nine children, have been killed by security forces, and hundreds more have been injured.

Iran’s Tasnim news agency said on Saturday that at least 200 “riot” leaders had been arrested.

Amnesty International slammed a “blanket internet shutdown” imposed by the Iranian authorities, saying it aimed to “hide the true extent of the grave human rights violations and crimes under international law they are carrying out to crush” the protests.

Iran’s attorney general, Mohammad Movahedi Azad, on Saturday warned that anyone taking part in protests will be considered an “enemy of God”, a death penalty charge, state television reported.

Iran’s ‍elite Islamic Revolutionary Guard Corps (IRGC), which operates separately from the army, also warned that ​safeguarding ‍the 1979 revolution’s ‍achievements and the ⁠country’s security was a “red line”, ​state ‌TV reported.

US, Iran trade barbs

Meanwhile, United States President Donald Trump reiterated support for the Iranian demonstrators, writing on social media on Saturday afternoon that Washington “stands ready to help”.

Trump’s post came a day after he warned the Iranian authorities against cracking down on the protesters, telling reporters that “if they start killing people like they have in the past, we will get involved”.

“That doesn’t mean boots on the ground, but it means hitting them very, very hard – where it hurts,” the US president said.

The US-based son of Iran’s deposed shah has also urged Iranians to stage more targeted protests, with the aim of taking and then holding city centres.

“Our goal is no longer just to take to the streets. The goal is to prepare to seize and hold city centres,” Reza Pahlavi said in a video message on social media, urging more protests on Saturday and Sunday.

Iranian Supreme Leader Ayatollah Ali Khamenei has called the demonstrators “vandals”.

In a speech broadcast on Press TV, Khamenei said Trump’s hands “are stained with the blood of more than a thousand Iranians”, in an apparent reference to Israel’s attacks on Iran in June, which the US supported and joined with strikes of its own.

Khamenei predicted that the “arrogant” US leader would be “overthrown” like the imperial dynasty that ruled Iran up to the 1979 revolution.

“Everyone knows the Islamic Republic came to power with the blood of hundreds of thousands of honourable people; it will not back down in the face of saboteurs,” he said.

Iranian Minister of Foreign Affairs Abbas Araghchi also accused the US and Israel of “directly intervening” to try to “transform the peaceful protests into divisive and violent ones”, claims a US Department of State spokesperson called “delusional”.

‘Underlying causes’

The demonstrations are the largest in Iran since a 2022-2023 protest movement spurred by the death in custody of Mahsa Amini, who had been arrested for allegedly violating the country’s strict dress code for women.

Reporting from Tehran on Saturday, Al Jazeera’s Tohid Asadi noted that while they started sporadically, the demonstrations have grown in recent days, particularly in the capital.

Asadi also explained that the government has been trying to control the situation by tightening security measures and introducing a new subsidy scheme for citizens.

But Mehran Kamrava, a professor of government at Georgetown University Qatar, said that the subsidy would do little to stem public frustrations over soaring costs of living.

“The inflation rate is at 42 percent, according to the government. Unofficially, it’s closer to 60 percent. So it doesn’t seem as if this kind of measure is going to alleviate any sort of economic pressure on the population,” Kamrava told Al Jazeera.

Ali Vaez, the director of the Iran Project at the International Crisis Group, said that even if the Iranian authorities can suppress the current protest movement, they will not be able to “address the underlying causes” of the unrest.

“[They are] only buying time until the next round of confrontation between the state and the society,” Vaez told Al Jazeera.