A Cairo court has charged an Egyptian national with spying for Iran.
Mr Dabbous described Iran as the "last bastion of Islam"
Prosecutors said Mahmoud Eid Muhammad Dabbous was paid by the Revolutionary Guard to provide information about a number of locations in Egypt.
Mr Dabbous pleaded not guilty and said Egyptian intelligence had tortured him while he was in detention.
Iran has not had formal diplomatic ties with Egypt since the 1979 revolution when Tehran broke off relations because of Egypt's peace treaty with Israel.
Mr Dabbous is also said to have made preparations for the assassination of a prominent Egyptian in return for $50,000.
He said the charges were an insult to Iran, "the last bastion of Islam".
"It is the target of the new globalisation. You know what is happening in Iraq, and Iran remains," he told reporters after the brief hearing.
"Whether we are Shia or Sunni, we are all in the same boat and we must defend ourselves."
The court also heard one charge against an Iranian diplomat, on trial in absentia, for giving Mr Dabbous money for information about the petrochemical complex in the Saudi port of Yanbu.
It said the information helped Mohammad Reza Hosseindoust - who is said to have fled Egypt - orchestrate an attack in Yanbu in May, in which five Westerners were killed.
Iran has denied the charges, describing them as "baseless".