Protection from a terror attack may cost Australians some freedoms: Abbott

Prime Minister Tony Abbott has warned Australians that the balance between freedom and security may have to shift to protect us from a terror attack.

Politicians returning to Canberra today came face to face with the danger, as armed police patrolled inside and outside Parliament.

With the threat of terror at the doorstep, armed Australian Federal Police covered every door.

They checked the Cabinet room and patrolled corridors. There is now restricted access to the ministerial wing and the gates into the courtyard the Prime Minister arrives and leaves by are now blacked out.

Mr Abbott addressed the threat in a 16-minute statement to the House of Representatives on national security.

"Regrettably, for some time, the delicate balance between freedom and security may have to shift," he said.

"I can never promise that hideous events will never take place on Australian soil. But I can promise that we will never stoop to the level of those who hate us        and fight evil with evil."

Mr Abbott justified the new anti-terror laws, promising they'll be overseen by agencies and parliamentary committees.

The Opposition supports the action in Iraq, but wants to study the anti-terror legislation.

"Military involvement to achieve humanitarian objectives is not our first instinct - it's never our preferred solution to geopolitical problems - but we recognise that sometimes there is simply no alternative," opposition leader Bill Shorten said.

To help ensure the legislation passes, the government has agreed to explicitly ban torture.

"The Australian Security and Intelligence Organisation does not practice torture and it never will," said ASIO chief Duncan Lewis.

Mr Abbott will head to New York tomorrow to address the UN Security Council about the threat. He hopes to have sideline talks with US president Barack Obama.