The announcement by the intelligence ministry came as nationwide protests entered their third week on Friday.
Dozens of people have been killed in heavy-handed responses to the protests that started when Amini, 22, died in custody three days after her arrest by morality police in Tehran for allegedly breaching the Iran's strict dress code for women.
Iran has detained a number of Iranians with dual citizenship over the years, accusing them of spying or otherwise undermining national security. Critics accuse Iran of using such detainees as bargaining chips to secure concessions from the international community.
A number of Europeans were detained in Iran in recent months, including a Swedish tourist, a Polish scientist and others. Two French citizens arrested in June are accused of meeting with protesting teachers and taking part in an anti-government rally.
Unrest also erupted on Friday in Iran's south-eastern Sistan and Baluchestan province, which borders Afghanistan and Pakistan and is often hit by attacks or clashes between security forces and armed groups, but it was not clear what was behind the violence.
Governor Hossein Khiabani told state television that 19 people were killed, including a colonel from the Islamic Revolutionary Guard Corps, during heavy gun battles, while provincial police chief Ahmad Taheri said three police stations were attacked.
Video shared by Iran International, a Persian-language television station based in London, showed men facing gunfire as they stoned a police station in Zahedan, the provincial capital.
The channel also reported bareheaded women chanting “death to the dictator” in the north-western city of Ardabil.
In the south-western city of Ahvaz, security forces fired teargas to disperse people who streamed on to the streets jeering and shouting anti-government slogans, in another video shared by Iran International.
The arrests of Europeans come as leaked government documents showed that Iran ordered its security forces to “severely confront” anti-government demonstrations that broke out last month, Amnesty International said on Friday.
The London-based rights group said security forces have killed at least 52 people since protests over Amini’s death began nearly two weeks ago, including by firing live ammunition into crowds and beating protesters with batons.
It said security forces have also beaten and groped female protesters who remove their headscarves to protest their treatment by Iran’s theocracy.
Irna, meanwhile, reported renewed violence in the city of Zahedan near the borders with Pakistan and Afghanistan. It said gunmen opened fire and hurled firebombs at a police station, setting off a battle with law enforcement.
It said police and passers-by were wounded, without elaborating, and did not say whether the violence was related to the anti-government protests.
The region has been the site of attacks on security forces claimed by militant and separatist groups.
Women have burnt their headscarves and cut their hair in the protests over Amini's death, announced September 16, that are the biggest seen in Iran since demonstrations in November 2019 over fuel price rises.
A leading Iranian human rights lawyer, Nasrin Sotoudeh, told US news magazine Time that she expected the protests to go on regardless of the intensity of the repression.
“What the people want is regime change, and no return to the past,” said Ms Sotoudeh, who is on medical furlough from a 38-year jail sentence for her advocacy work.
“And what we can see from the current protests and strikes that are now being initiated is a very real possibility of regime change.”
Iranian authorities have severely restricted internet access and blocked Instagram and WhatsApp, popular social media applications that are used by protesters to organise and share information.
That makes it difficult to gauge the extent of the protests, particularly outside the capital, Tehran. Iranian media have only sporadically covered the demonstrations.
Amnesty said it had obtained a leaked official document issued to the commanders of armed forces in all provinces on September 21 instructing them to “severely confront” protesters.
Another leaked document showed that on September 23, the commander of the armed forces in Mazandaran province, where some of the deadliest clashes have taken place, ordered security forces to “confront mercilessly, going as far as causing deaths, any unrest by rioters and anti-revolutionaries”.
The NGO said it had confirmed 52 deaths in the protests but the toll was likely to be higher.
Another rights group, Oslo-based Iran Human Rights, said 83 people were confirmed to have been killed, while Iran's Fars news agency has put the death toll at “around 60".
Many Iranian journalists, activists and other prominent figures have been arrested in the crackdown.
Former Iranian international footballer Hossein Maahini was arrested on Friday after supporting the protests on his social media accounts, state media said.
Iranian football fans, meanwhile, asked Fifa to ban their national team from this year's World Cup in Qatar because of the crackdown.
Security forces also arrested singer Shervin Hajipour, whose song Baraye, made up of tweets about the protests, went viral on Instagram, the rights group Article 19 said.
His song, which racked up millions of views, has now been removed from his Instagram account.
The government's violent response has drawn widespread condemnation.
Demonstrations of solidarity with Iranian women have been held worldwide, and rallies were planned in 77 cities on Saturday.
Iran has blamed outside forces for the protests, and on Wednesday it launched cross-border missile and drone strikes that killed 14 people in northern Iraq's Kurdistan region, accusing Iranian Kurdish rebel groups based there of fuelling the unrest.
The IRGC pledged to carry out more attacks until the groups are disarmed.
The US said one of its citizens had been killed in the Iranian strikes.
— With reporting from agencies.