Amnesty International says in a statement that Faleh Abdullah al-Mansuri, Rasool Mezrea, Jamal Obeiwadi, and Taher Ali Mezrea are believed to be being held incommunicado at an unknown location in Iran, and may be at risk of torture.
The four were arrested by political security officers in Damascus on May 11.
Amnesty International says most of them are said to have UN refugee status and that one -- al-Mansuri -- has Dutch nationality. The group says Dutch authorities reportedly informed al-Mansuri's son of his father's forcible return to Iran on August 9.
Most Iranian Arabs live in Khuzestan province, which borders Iraq to the east. Tensions have been mounting in the province, with hundreds of people being reportedly arrested in recent months.