Up to 60 Islamic extremists are actively involved in terrorist cells in Australia, the federal police commissioner confirmed Wednesday after a former spymaster claimed it was only a matter of time before an attack was launched on Australian soil.

Michael Roach, a senior official who recently retired from the Australian Security Intelligence Organization, or ASIO, said Australia was facing an imminent risk of a terrorist attack, and called for more extreme counterterrorism powers.

He said Australia’s two largest cities, Sydney and Melbourne, were playing host to groups of Islamic extremists who had received specialized training from terrorist groups overseas.

“Perhaps the number is around 50 or 60 in Australia that are working in separate cells,” Roach told the Australian Broadcasting Corporation late Tuesday. “The threat is real. It’s a matter of when this (an attack) will happen.”

The would-be terrorists had developed a high degree of “precision” in their methods of assault, Roach said, and police and security officers of the public should be allowed to target men of Middle Eastern appearance if they were behaving suspiciously.

“Unfortunately, Middle Eastern people are going to be approached more often than not,” Roach said.

“But if that person has nothing to fear, nothing to hide, and is just being approached politely, that person by rights should not be concerned.”

Mick Keelty, the commissioner of the Australian Federal Police, or AFP, confirmed Roach’s allegations about the number of suspected terrorists operating in Australia, saying the figures were “not news to the intelligence community.”

“We’ve been aware for some time roughly the number of people who have trained overseas and they’ve been the focus of the attention of both ASIO and the AFP and also the state police in our joint operations,” Keelty told the ABC on Wednesday.

He disputed Roach’s profile of the suspected terrorists however, saying it would not be constructive for police to target Middle Eastern people.

“One of the things that I fear is that we are marginalizing the Islamic community by broadbrush stereotyping,” he said.

“We are focused on the people who we are aware have trained overseas, we are focused on the people who we know have a propensity to do something wrong. We’re not focused on the Islamic community.”

He also said Australian police and intelligence agencies were reviewing their counterterrorism powers in the wake of the July terrorist attacks on London’s public transport system, but would not elaborate on what reforms they are seeking.

“The reality is this is a moving feast — we are challenged by different moves by the terrorist groups, by each interest group, every time they attack,” he said.

“We have to increase our understanding and we have to appropriately respond but let me say this … it’s the appropriateness of the response that we have to be careful about.”