Ayatollah Mahmud Hashemi Shahroudi was receiving medical treatment for a reported brain tumor at a private hospital in the northern German city of Hanover, when several cases were lodged against him stating that the top Iranian cleric was guilty of murder and crimes against humanity.
Shahroudi served as head of Iran's justice ministry from 1999 to 2009. During this period, an estimated 2,000 Iranian prisoners, including many minors, were executed.
German politician Volker Beck, who filed one of the complaints, told DW that "Germany should not be a haven for criminals."
"I also wonder how a man like Shahroudi could even get a German visa," he added.
The filing of the cases prompted the Iranian cleric to abruptly end his stay in Germany and fly back to Iran on Thursday, January 11.
The incident drew sharp reactions from Iranian social media users across the world, with some lambasting the German government for allowing the ayatollah to go scot-free.
The hashtag #Shahroudi is being used by Iranian critics to post their views on the issue. One Iranian Twitter user named Sam Vaseghi expressed his anger at Germany's inaction, saying: "Gabriel (Germany's Foreign Minister Sigmar Gabriel) arbitrarily gave an assurance to the Iranian government that Shahroudi would return safely to Iran following his medical treatment."
Another user tweeted: "Shahroudi's case shows that there is no safe haven in the world for criminals."
Some Iranians also used the hashtag #ShameonGermanGov to voice their disappointment.
A user named Farhang posted: "For several years, I was praising your country (Germany). Today I noticed I was wrong. You betrayed millions of people- again."
Another user, Ramyar Hassani, who is a Kurdish activist in exile wrote: "European Foreign Policy towards Iran: Begging for the release of its innocent civilians from torture in Iran, meanwhile, providing best medical treatment to Ayatollahs who committed crime against humanity and escorting them back to Tehran."
Likewise, Ramin Dehghan tweeted: "Germany, you mat [might] have won the trust of a regime, but you lost the respect of nations. People are waiting!"
Another user named Majid posted on Instagram: "Money has more power than justice even in Germany, which is a democracy and governed by the rule of law."
Facebook user "Hamebaham Iranian" wrote: "Didn't you expect it from Germany? Since years Germany has been turning a blind eye towards Iranian state criminals. Shame on you Germany!"
Some users also wrote sarcastic comments, for instance tweeting an imaginary conversation between Iranian Foreign Minister Javad Zarif and his German counterpart Gabriel, in which a deal was struck for the safe return of Shahroudi to Tehran in exchange for German firms receiving commercial favors.
However, not everyone agrees with this criticism. For instance, a Twitter user by the name of Sizdah wrote: "Those who are shouting for Shahroudi's arrest and believe 'Germany will not tarnish its relations with Iran over him' do not have the right view on an independent justice system, where judges do not care about the political and diplomatic interests. Don't you remember the American judge who ruled against Trump's travel ban?"