"No circumstances justify resorting to inhumane acts and creating terror in the name of the Divine religion of Islam,” said Iranian Foreign Ministry spokeswoman Marzieh Afkham on Monday.
She noted that the Australian police had been completely aware of psychological status of the hostage taker, who had immigrated to Australia about 20 years ago.
Local media have identified the hostage taker as an Iranian national.
Some blame the incident on parties supporting terrorism, including Israel, the United States, and certain regimes in the Middle East region that back such terrorist groups as al-Nusra Front and the Islamic State in Iraq and the Levant (ISIL).
In a message posted via his Tweeter account on December 1, the hostage taker had spoken defiantly of Iran and the supporters of the Syrian President Bashar al-Assad as terrorists.
Australian security forces raided the Lindt Café in Sydney’s central business district on Monday to end the siege that lasted over 16 hours.
The gunman and two hostages were killed in the rescue operation, according to police sources.
Australia has been on high alert in recent months after the Canberra government raised concerns over the return of the citizens who had joined terrorists fighting in Syria and Iraq.
Canberra said earlier this month that at least 20 Australian nationals fighting for terrorist groups had been killed in the two neighboring Arab countries. Officials report that 90 Australians have joined ISIL militants there.