Iran's foreign ministry on Monday summoned Germany's ambassador over tweets condemning the execution of Navid Afkari, a wrestler accused of murdering a man during a wave of anti-government protests in 2018.
The ministry "strongly condemned" the tweets and told German envoy Hans-Udo Muzel that the reaction was considered to be an "interference in the internal affairs" of Iran, an official statement read.
It called on the German embassy to "recognize the limits of its diplomatic duties and not go beyond them."
"Interference in the laws, regulations and judicial procedures of the Islamic Republic of Iran is not tolerable in any way," the statement added.
Afkari, a 27-year-old wrestler, was executed at a prison in the southern city of Shiraz on Saturday.
According to Iran's judiciary, he had been found guilty of "voluntary homicide" for stabbing to death a water department employee on August 2, 2018.
Shiraz and several other urban centers across Iran had been the scene that day of anti-government protests and demonstrations over economic and social hardship.
The German embassy condemned Afkari's death in a message written in Farsi posted on its official Twitter account on Sunday.
"We were deeply shocked by the execution of Navid Afkari," the message read.
"It is not acceptable that basic legal rights be ignored in order to silence opposing voices," it added.
The embassy said that Afkari's two brothers "are still in prison and now they need our solidarity."
Reports published abroad say Afkari was convicted on the basis of confessions aired on television after being extracted under torture, prompting online campaigns for his release.