Australian authorities have arrested up to 15 people in a massive counter terrorism pre-dawn raid on Thursday in light of reports of an impending public execution by sympathizers of the Islamic State of Iraq and Syria (ISIS).

The security exercise, which included over 800 officers, was centered in Sydney and Brisbane. Reports indicate that some of the suspects have been released over the course of the day.

According to Prime Minister Tony Abbott, the country's security agencies were acting on intelligence reports that local terrorist networks associated with ISIS have been directed to stage 'demonstration killings.'

PM Abbott revealed that the exhortations came "from an Australian who is apparently quite senior in ISIL." Reports indicate that some of the suspects still in the custody of the police have been able to positively identify the suspected terrorist commander, Mohammad Ali Baryalei. The police has since issued an arrest warrant for the suspect

Officials have expressed concerns that the 50+ Australians believed to be among the ranks of the terrorists are working to rally a support base at home. Last week, the police arrested two men who were charged with being ISIS facilitators.

Last week, PM Abbott raised the country's terrorist alert level to high for the first time in more than a decade. Although he stressed that there were "no specific intelligence of particular plots," he noted that "we do have intelligence that there are people with the intent and the capability to mount attacks."

The Australian PM has announced that his country will donate 600 soldiers to support the air strikes against the ravaging terrorists, who already control large parts of Syria and swatches of northern Iraq.

However, he noted that due to certain 'legalities' the operations of Australian forces will be limited to Iraq.