ISIS has called for more terror attacks during the holy month of Ramadan using the secretive messaging app Telegram, reports Mirror Online.
The audio message distributed on Monday was believed to have been issued by Islamic State`s official spokesman Abi al-Hassan al-Muhajer.
It praised a recent attack in the Iranian capital last week.
Suicide bombers and gunmen left 17 people dead after targeting the parliament building and a mausoleum in Tehran.
"O lions of Mosul, Raqqa, and Tal Afar, God bless those pure arms and bright faces, charge against the rejectionists and the apostates and fight them with the strength of one man," said al-Muhajer.
Rejectionist is a derogatory term used to refer to Shi`ite Muslims.
"To the brethren of faith and belief in Europe, America, Russia, Australia, and others."Your brothers in your land have done well so take them as role models and do as they have done."
Telegram Messenger has become a favoured tool of terrorists to disseminate propaganda due to its impenetrable security.
Groups such as ISIS can distribute material on channels anonymously without fear of being traced for spy agencies.Telegram insists it takes action against Islamic State posts on its `Channels`.
It recently responded to calls for the service to give security agencies `backdoor` entry with a blog post insensitively titled `Don`t shoot the messenger`.
The company, created by two Russian brothers Pavel and Nikolai Durov, said: "Telegram is unique among encrypted messengers in that it has Channels - a tool for sending open public messages to unlimited audiences. "
"Naturally, terrorists have tried to use this tool for ISIS-related broadcasts as well."But just like other networks, Telegram took steps to kick them off this public platform.
"Terrorist public channels still pop up – just as they do on other networks - but they are reported almost immediately and are shut down within hours, well before they can get any traction. (Seen something? Report it now!)
"And yet, no matter how hard Telegram and the others are trying, terrorists have a powerful ally that helps them spread their horrible message far and wide."
The Muslim holy month of Ramadan began on 26 May and ends on June 24. ISIS has previously called for increased attacks during Ramadan .