Majidreza Rahnavard was hanged "in public" early on Thursday in the city of Mashhad, the judiciary announced, reports BBC.

A court convicted him of the charge of "enmity against God" after finding he had stabbed to death two members of the paramilitary Basij Resistance Force, the British media reported.

Mahmood Amiry-Moghaddam, director of Norway-based Iran Human Rights, reacted to the development in the country and posted on Twitter: " Public execution of a young protester, 23 days after his arrest, is another serious crime committed by the I.R. leaders and a significant escalation of the level of violence against protesters."

UK Foreign Secretary James Cleverly warned at the time that the world could not "turn a blind eye to the abhorrent violence committed by the Iranian regime against its own people", reports UNI.

Iran witnessed protests after the death of 22-year-old  Mahsa Amini.

She was detained by the country's morality police in September and died while in custody.

She was held for allegedly wearing her hijab, or headscarf, "improperly", media reports said.

The unrest, which began in the capital Tehran where Amini died, has spread to some 160 cities in all of Iran's 31 provinces.

It is considered one of the most serious challenges to the Islamic Republic since the 1979 revolution.