(CNN) -- Iranian authorities have buried the body of a political prisoner, who was executed last week, without the presence of his family or friends, his son told CNN.
Ali Saremi's body was buried over the weekend at the Amir-Abad village in Boroujerd, nearly 400 kilometers southwest of Tehran.
"The authorities never informed my family about my father's execution and now the government has barred us from holding any kind of funeral service," his son, Akbar Saremi, said.
Ali Saremi was hanged for "fighting against the sacred Islamic Republic of Iran system and launching antagonist propagations," Iranian state-run media reported at the time of his execution Tuesday.
Iranian authorities allege that Saremi was a member of the People's Mujahedeen of Iran, also known as the Mojahedin-e Khalq Organization, which has opposed the Iranian government for decades.
Tehran considers the group to be a terrorist outfit, as does the United States. The European Union does not.
Members of the Friends of a Free Iran group condemned Saremi's execution Tuesday, calling it "another crime for which the mullahs will be held to account when freedom is finally restored to that beleaguered nation."
The group also demanded that Iranian leaders "be tried in the International Court of Justice for crimes against humanity."
Ali Saremi had been arrested five times since 1982. His latest arrest came in 2007 after visiting his son at Camp Ashraf, a refugee community in Iraq that is home to an estimated 3,500 exiled members of the Mujahedeen, Akbar Salemi told CNN.
Saremi was arrested for his alleged presence at anti-revolutionary gatherings organized by the People's Mujahedeen and for sending information for the group, according to Iranian state media reports.
Akbar Salemi denied those allegations, saying his father's "only interest in Mojahedin-e Khalgh (MEK) and Camp Ashraf was to visit me, and that's the last time I saw my father."
"This is a very difficult time for my family," Akbar Saremi said, adding that other family members are being targeted now.
"My cousin is still being detained after he displayed a picture of my father on the door of the family home as a sign of mourning," Saremi said.
Other family members were detained last week as they gathered outside the prison where Ali Saremi was hanged. They have since been released.