The Mizan news agency, which is affiliated with the judiciary, said Moshen Shekari was hanged on December 8 after his appeal against his sentence was rejected by Iran's Supreme Court.

Shekari was accused of brandishing a weapon with the "intention of killing and causing terror and depriving the freedom and security of people," as well as "intentionally injuring" a security officer with a weapon and "blocking the street."

Shekari was one of thousands of Iranians to take to the streets nationwide since Amini died while in police custody in September. She was being held for allegedly wearing a head scarf improperly.

The government has launched a brutal, and often deadly, crackdown on demonstrators, while lawmakers have pushed for harsh punishments to try and quell what has become the biggest challenge to the country's leadership since the Islamic revolution in 1979.

Rights groups and Western governments have warned Tehran about issuing death sentences to protesters after hasty trials some have called "sham" justice.

U.S. State Department spokesman Ned Price called the execution a "grim escalation in the Iranian regime's attempt to suppress dissent" and vowed that the clerical regime would be held to account.

Price said earlier this week that the death sentences were a tactic in the regime's "brutal crackdown on what can only be described as peaceful protesters -- individuals who are exercising their universal rights."

The sentences are meant to intimidate people and "simply underscore Iran’s leadership’s fears of its own people and the fact that Iran’s government fears the truth,” he said.

Jake Sullivan, President Joe Biden's national-security adviser, reacted to the execution of Shekari on Twitter.

"The unjust and cruel execution of #MohsenShekari is a cynical attempt to intimidate the brave Iranian people. Our hearts are with his family. We will hold the Iranian regime accountable for the brutal violence it’s committing against its own people," he said.