Amir Hossein Hatami, 18, was sentenced to death in February along with six others by a Tehran revolutionary court and was hanged at dawn in the notorious Ghezel Hesar prison outside the capital, according to Norway-based NGO Iran Human Rights.
The Iranian judiciary's Mizan Online website said he acted "against national security" on behalf of Israel and the United States by breaking into "a military centre and destroying it in order to seize the weapons stored there" during the protests.
He is the fourth man to be executed over protests that broke out in Iran in late December against the rising cost of living before evolving into nationwide anti-government demonstrations. The protests peaked on January 8 and 9 and were met with a crackdown that activists say left thousands dead.
On March 19, authorities executed three men convicted of killing police in the protests, including 19-year-old Saleh Mohammadi, a wrestler who took part in international competitions.
This week, authorities have hanged four men convicted on charges of rebellion for membership in the banned People's Mujahedin of Iran (MEK) after their sentences were upheld by the supreme court.
Amir Hossein Hatami "was subjected to torture and sentenced based on forced confessions in a grossly unfair trial before the revolutionary Court", said IHR director Mahmood Amiry-Moghaddam.
"In the past two weeks alone, three protesters and four political prisoners have been executed, and hundreds more remain at imminent risk," he added.
The seven were accused of setting fire to a base belonging to the Basij militia -- a volunteer force of the Revolutionary Guards -- in Tehran during the protests.
But defence lawyers accused plainclothes forces of trapping protesters inside a building, locking the doors, and themselves starting the fire.
-'Unconscionable'-
Amnesty International had in a statement on Wednesday warned that the lives of Hatami and his six co-defendants were at risk.
"It is unconscionable that even as the population is reeling from conflict and mass bereavement amid the ongoing aerial bombardment by Israel and the US, the authorities continue to weaponize the death penalty to eradicate dissenting voices and further terrify people," said Amnesty's deputy director for the region, Diana Eltahawy.
IHR said the seven men had been convicted in the fast track trial -- just a month after their arrest -- by the court presided over by the notorious judge Abolqasem Salavati.
Salavati was sanctioned in 2019 by the United States, which said he is known as the "Judge of Death" for his frequent death sentences.
The executions came amid Iran's war with Israel and the United States which erupted on February 28 with strikes that killed the Islamic republic's supreme leader, Ali Khamenei.
The US-based Human Rights Activists News Agency (HRANA) recorded more than 7,000 killings in the protests, the vast majority of them protesters, and said the toll could be far higher.
Tehran has acknowledged that more than 3,000 people died during the unrest, including members of the security forces and innocent bystanders, and has vowed no leniency for those it says were behind "terrorist acts".