New South Wales police contacted Dr Jamal Rifi to notify him that a twitter account linked to Mohamed Elomar had made threatening posts directed at the western Sydney community leader.
Dr Rifi is one of many who publicly condemned shocking Twitter images from Syria posted by Australian Khaled Sharrouf.
Mohamed Elomar is another Australian fighting overseas and he offered $1000 bounty as reward for information on Dr Rifi and his family's whereabouts.
NSW police are monitoring the situation, and the twitter post offering the bounty has been deleted.
Dr Rifi says he won't be silenced from speaking out against those from his community committing atrocities in Syria and Iraq.
"There is a misconception out there that I am the only one who is speaking against this group. That's not true."
Dr Rifi names the Grand Mufti Professor Ibrahim Abu Mohammed, the Islamic Council of Victoria and the Lebanese Muslim Association as expressing similar views as him.
"Why I am being singled out I don't know."
Dr Rifi also responded on twitter writing: "these keyboard warriors do not scare me. To know my address just ask your dad we were in the same soccer team".
Dr Rifi is not toning down his comments.
"These people pretend that they are over there defending Islam. They are over there distorting the message of Islam," says Dr Rifi.
Both Khaled Sharrouf and Mohamed Elomar have warrants for their arrest issued by the Australian Government.
While mainstream muslim leaders are speaking out against IS, others are criticising the media coverage targeting their community.
Following this week's Insight program hardline group Hizb ut-Tahrir told SBS the focus on IS supporters here is sensationalist and out of proprotion. They say it should be seen as symptomatic of a wider problem with resentment over Western foreign policy.
In the broader region, Australia's neighbour Indonesia is staging a crackdown on IS sympathisers - saying 50 Indonesians have gone to Iraq and Syria.
Ansyaad Mbai, Head of the Indonesian National Counter Terrorism Agency, says: "If we don't act against this it will only revive terrorism in our country. We are the ones that suffer not Iraq."
Professor Damien Kingsbury from the School of International and Political Studies at Deakin University says Australia could also be effected.
"Really what we're seeing is a new generation of jihadi Islamists in Indonesia. They've gone off now, the question is what happens when they come back?" he says.
"The real threat I think is in Indonesia but it certainly could be directed towards Australians or Australian interests in Indonesia as we've seen in the past."