Iran slammed its arch enemy the United States for hosting Sharmahd and "supporting known terrorists who have claimed responsiblity for several terrorist acts inside" the country.
The Intelligence Ministry called it a "complex operation", without elaborating.
Iran has arrested Jamshid Sharmahd, alleged ringleader of the Tondar ('Thunder') terrorist group, the Ministry of Intelligence announced on Saturday.
It said Iranian intelligence aborted several other plots in more recent years, including blowing up the shrine of Ayatollah Ruhollah Khomeini, the late founder of the Islamic Republic. The group's founder disappeared in the mid-2000s.
Iranian state media published a photo purportedly of Sharmahd.
In 2010, a suspected Iranian operative vanished before facing trial in California for allegedly trying to hire a hitman to assassinate Sharmahd.
While it was not clear how Iran captured Sharmahd, its operatives are known for using family members and tricks to lure exiles back to Iran or to Tehran-friendly countries.
A 2010 US diplomatic cable from London later published by WikiLeaks shows that a Voice of America commentator said that same operative earlier had been in contact with him.
According to the group's website, Sharmahd is an electronics engineer born in 1955. "Because we have heard that once upon a time some people were living in the region who were able to build an empire". The US does not classify the group as a terrorist organisation, and has reportedly allowed it to freely operate from its home base in Los Angeles, California, where it runs radio and television stations calling for the violent overthrow of the Iranian government.
Iran's Defense Ministry said the Etka company has opened the supermarket in Caracas offering Iranian products.
The Iranian foreign ministry said in a statement the USA "must be held accountable for backing this terrorist group and other groups and criminals responsible for sabotage, armed and terrorist operations [.] from within the United States and shedding the blood of Iranian citizens".
Suspicion long has fallen on Israel for a string of assassinations targeting scientists amid concerns about Iran's nuclear programme, which the West fears could be used to develop a nuclear bomb. Iran long has maintained its program is for peaceful purposes.
The arrest comes amid growing tensions between Washington and Tehran. A series of incidents previous year were capped by a USA drone strike in January killing a top Iranian general in Baghdad.