(VOA) -- Seven teenagers in Australia have been arrested in a sweeping anti-terrorism operation in the wake of last week's stabbing attack of a bishop in Sydney.

New South Wales Deputy Commissioner David Hudson told reporters Wednesday that more than 400 federal, state and local authorities were involved in the operation. He said the suspects, who are between 15 to 17 years old, were associates of the 16-year-old boy charged in the April 15 attack on Assyrian Bishop Mar Mari Emmanuel during a service that was streamed live online.

Emmanuel was seriously injured in the attack. The suspect has been charged with committing a terrorist act.

Hudson said their surveillance of the group showed they believed in a religiously motivated violent ideology, and posed an imminent threat to the community that law enforcement would not be able to prevent, calling it an "unacceptable risk."

He said five other teenagers were detained in the raids and are under questioning.

Australian Federal Police Deputy Commissioner Krissy Barret said the investigation had not uncovered any evidence of specific targets or a specific time for an attack.

The Australian Security Intelligence Organization, the nation's main domestic spy agency, was also involved in the investigation.