Iranian security agents arrested at least eight people linked to the US Central Intelligence Agency during last week's unrest over gasoline price hikes, the official news agency IRNA reported on Wednesday.
"These elements had received CIA-funded training in various countries under the cover of becoming citizen-journalists," IRNA quoted the Intelligence Ministry as saying. "Six were arrested while attending the riots and carrying out (CIA) orders and two while trying to ... send information abroad."
Iran's supreme leader Ayatollah Ali Khamenei on Wednesday said his sanctions-hit country had foiled a "very dangerous" plot after the violent demonstrations.
New York-based Human Rights Watch, meanwhile, accused Tehran of "deliberately covering up" more than 100 deaths and thousands of arrests during the crackdown.
The demonstrations first flared on November 15, hours after a midnight shock announcement that petrol prices would immediately go up by as much as 200 percent in the Islamic republic.
A near-total internet blockout was imposed as the protests turned violent, with police stations attacked, petrol pumps torched, and shops looted.
Connectivity was restored for much of the country after the unrest was quashed within days, and mobile access was returning late Wednesday.
The outage had apparently been enforced to temper shows of dissent and stem the flow of videos of violence being shared online.
But it also made it difficult to know the full extent of the bloodshed.
Officials in Iran have confirmed five people were killed and so far announced about 500 arrests, including of some 180 "ringleaders".
London-based Amnesty International said on Monday that 143 people were killed and up to 7,000 arrested, citing what it said were "credible reports".
- Foreign enemies -
Iran has blamed the unrest on "thugs" backed by its foreign enemies, including the US, Israel and the People's Mujahedeen of Iran, an exiled armed opposition group it considers a "terrorist" cult.
"The people foiled a deep, vast and very dangerous conspiracy on which a lot of money was spent for destruction, viciousness and the killing of people," Khamenei said, quoted on state television.
The leader was speaking at a gathering of the Basij, a loyalist militia which he advised to have a presence in all districts of Iran and to remain a step ahead of the enemy.
On Twitter, Khamenei expressed his "heartfelt gratitude and appreciation" to the Iranian nation in a post that featured pictures of a massive pro-government rally held Monday in Tehran.
"The people proved again that they are powerful and great, and defeated the big conspiracy of the enemy with their presence on the scene," he said.
"Police and security forces... performed their duty, but what the nation did during this week was more important than any other measure," said another tweet.
The tweets accused the "#GlobalArrogance and #Zionism" -- Iran's arch-enemies the US and the Jewish state -- of being behind the street violence.
- 'Fear and retribution' -
The United States said it had received thousands of messages from Iran about protests after appealing to demonstrators to defy the internet restrictions.
"We've received to date nearly 20,000 messages, videos, pictures, notes of the regime's abuses through Telegram messaging services," Secretary of State Mike Pompeo said, referring to the encrypted app.
Long-fraught links between Tehran and Washington plunged to a new low in May last year when the US unilaterally withdrew from an international accord that gave Iran relief from sanctions in return for curbs on its nuclear program.
In its report released in Beirut, Human Rights Watch accused Iran of "deliberately covering up the scale of the mass crackdown against protesters".
HRW called on Iranian authorities to "immediately announce the number of deaths, arrests, and detentions... and permit an independent inquiry into alleged abuses".
Its deputy Middle East director, Michael Page, criticized Iran for having so far "refused to provide an accurate death toll and instead threatened detainees with death".
"Keeping families in the dark about the fate of their loved ones while ratcheting up an atmosphere of fear and retribution is a deliberate government strategy to stifle dissent," Page said.
The unrest erupted after the price of petrol was raised by 50 percent for the first 60 liters and 200 percent for any extra fuel after that each month.
The government says the proceeds will go to poor families.