CANBERRA - Australian police and intelligence agencies are keeping tabs on as many as 60 known terrorists operating within the country.

The estimate, made by a former counter-terrorism chief, has been confirmed by Australian Federal Police Commissioner Mick Keelty and comes as fears mount of an attack on the continent.

A poll shows Australians overwhelmingly reject the Government's claim that involvement in Iraq has not increased the risk to the country, and want even tougher laws to protect them.

But there are growing concerns that the fear of terrorism will trigger a violent backlash against Muslims, underlined by plans that could see them becoming subject to random searches and other measures.

The latest specific warning of the danger to Australia was made by Michael Roach, who retired two years ago as an assistant director with the domestic spy agency, the Australian Security Intelligence Organisation, responsible for the security of government facilities.

He told ABC television's Lateline that a network of Islamic terrorists was operating in Sydney and Melbourne, most of them known to ASIO.

"Perhaps the number is around 50 or 60 in Australia, who are working in separate cells," he said.

"The threat is real. It's a matter of when will this happen.

"They have precision with regard to their planning, their techniques and their methodologies.

"They are divided into groups within the cell structures, for example, having the co-ordinator of the group down to those people who will actually deliver the bomb."

Roach's claim was supported by Keelty, who said the estimate of the number of terrorists at work in Australia was not news to the intelligence community or police.

"We've been aware for some time of roughly the number of people who have trained overseas and they've been the focus of the attention of both ASIO and the AFP [federal police], and also the state police in our joint operations."

Keelty said the suspects had been the focus of a number of agencies "for the past few years".

"A lot of good hard work has been put into this and we are steadily keeping on top of it," he said.

ASIO has consistently warned of attacks and has blocked dozens of people suspected of links with terror groups from entering the country.

Anti-terror agents have uncovered plans to attack national landmarks in Sydney and Melbourne, and charged a number of people with terror-related offences.

The Government has listed 18 groups under legislation that bans any links to, support for, or membership of, extremist organisations.