Amnesty International has condemned the Iranian authorities for publicly flogging a man who was convicted of consuming alcohol when he was 14 or 15.
Local media published photographs of the man - identified only as "M R" - being given 80 lashes in a square in the eastern city of Kashmar on Tuesday.
Prosecutors say he was arrested in the Iranian year of 1385 (March 2006-March 2007) and sentenced the next year.
It is not clear why the punishment was carried out more than 10 years later.
The photographs show a young man tied to a tree being flogged by a masked man in uniform. A small crowd of people can be seen watching at a distance.
"The circumstances of this case are absolutely shocking, representing another horrific example of the Iranian authorities' warped priorities," Amnesty's Middle East and North Africa Director, Philip Luther. said in a statement.
"No-one, regardless of age, should be subjected to flogging; that a child was prosecuted for consuming alcohol and sentenced to 80 lashes beggars belief."
The Young Journalists Club website quoted Kashmar's prosecutor as saying M R consumed alcohol at a wedding where an argument caused a fight in which a 17-year-old boy was killed. He was not suspected of involvement in the death.
Article 265 of Iran's Islamic penal code states that the punishment for consumption of alcohol by a Muslim is 80 lashes.
More than 100 other offences are punishable by flogging, including theft, assault, vandalism, defamation and fraud, as well as acts that Amnesty said should not be criminalised, such as adultery, intimate relationships between unmarried men and women, "breach of public morals" and consensual same-sex sexual relations.
Mr Luther said Iran should abolish all forms of corporal punishment.
As a party to the International Covenant on Civil and Political Rights, the country was legally obliged to forbid torture and other cruel, inhumane and degrading treatment or punishment, he noted.
"It's simply unacceptable that the Iranian authorities continue to allow such punishments and to justify them in the name of protecting religious morals."
In 2014, six Iranians were sentenced to prison and 91 lashes after being arrested for appearing in a video dancing to Pharrell Williams' song Happy.