Australian security officials say they stopped a suspected plan by Islamist extremists to capture random citizens and behead them in public and on camera.

More than 800 security personnel raided 25 homes across two cities early yesterday morning in what authorities said was the largest counterterrorism raid ever conducted in Australia.

Authorities said they arrested 15 suspects, one of whom, Omarjan Azari,  22, appeared in a Sydney courtroom later in the day. The raids also resulted in the seizure of computers, documents and a firearm.

Australian Prime Minister Tony Abbott told reporters that intelligence showed the directive for the attack came from an Australian who holds a senior position in the Islamic State, the terrorist group also known as ISIS or ISIL.

Last week, Abbott announced that his nation’s terrorism-alert level had been raised from medium to high.

Nile Gardiner, a leading authority on transatlantic relations at The Heritage Foundation, complimented Australia for acting quickly to stop the alleged terror plot.

“Australia’s highly effective anti-terror raids are a reflection of the fact that the free world is engaged in a global war against a vicious Islamist enemy that seeks our destruction,” Gardiner said.

He credited Abbott with “decisive leadership.”

On the same day as the raids, Australia extended its participation in the fight against the Islamic State, sending 200 special forces troops to the United Arab Emirates as part of a U.S.-led coalition against the terrorist group in Syria and Iraq.

Australia estimates that 60 of its citizens are fighting for militant groups in the Middle East and 100 more support extremist groups from within Australia, the Associated Press reported.

Helle Dale, a Heritage Foundation senior fellow, said:

The arrests by Australian authorities of terrorist plotters planning savage attacks on Australian citizens shows both the ambitions and the limitations of the ISIS terror and propaganda strategy. The group persuaded unhinged individuals to heed its calls to murder, but vigilance, intelligence and good police work won the day.