Members of Calgary's Muslim community say they're alarmed and frustrated at the news two more Canadians have joined the ranks of the jihadist group ISIS, and they're calling on the federal government to do more about the radicalization of youth.

CBC News reported exclusively on Thursday that Greg and Collin Gordon, who converted to Islam and became known to members of Calgary's Muslim community as Abdul Malik and Khalid, had joined the ranks of foreign fighters with the Islamic State of Iraq and Syria. The brothers disappeared sometime in late 2012.

"This is getting very serious," Calgary Imam Syed Soharwardy told CBC News. "In my opinion the government has to put up more resources to monitor the activities of those who are recruiting, those who are getting recruited and those who are coming back.

"My biggest nightmare is those who are coming back."

Between 2011 and 2012, they shared an apartment in the same downtown Calgary highrise that once housed Damian Clairmont and Salman Ashrafi.

Ashrafi has been identified as a suicide bomber in an ISIS operation in Iraq last November that took the lives of 46 people. Clairmont was killed fighting in Syria earlier this year.  

'My biggest nightmare is those who are coming back.' - Calgary Imam Syed Soharwardy on jihadist threat

Another Calgarian, Farah Shirdon, who once attended a "study group" with Ashrafi, Clairmont and the Gordon brothers, joined ISIS and was reported to have been killed in battle a few weeks ago.

In a report issued on Friday the federal Department of Public Safety said the RCMP are developing an early intervention program to deal with what it calls "extremist travellers." Police officers will partner with community groups to work with youth, but the program won't start until later this year.

Prof. Michael Zekulin, who studies terrorism and radicalization at the University of Calgary, says the Canadian government has been slow off the mark.

"Canada is lagging behind in terms of any coherent strategy, yes," he told CBC News.

However, Muslim leaders in Calgary want to keep the issue on the agenda. They are planning a four-day conference about radicalization, entitled "Own It," in September.