Will not rest till Australians safe: Abbott

Prime Minister Tony Abbott today ordered a review into a deadly hostage crisis in Sydney that left two persons dead and vowed not to rest until he was assured Australians were safe.

Abbott said that the Commonwealth and New South Wales governments will urgently conduct a review into the siege.

"In the aftermath of the horrific Martin Place siege and following the tragic loss of innocent lives, we must learn what we can from this incident and implement any changes necessary at the State and Federal level," he said, adding the report of the review will be submitted by January end.

"I will not rest until I am confident that you are as safe as any government can possibly make you," he said.

Noting that the review will identify important lessons for the future, Abbott said it will examine and make recommendations about a wide range of issues including the circumstances surrounding hostage-taker Haron Monis' arrival in Australia and subsequent granting of asylum and citizenship to him.

"As we work to learn what we can from these terrible events, we acknowledge once again the courage and professionalism shown by our law enforcement and security agencies and emergency services" Abbott said.

"We are determined to ensure that nothing stands in the way of ensuring the people who put their lives on the line to keep Australia safe can get their job done," he said.

Abbott earlier vowed a transparent probe into why Monis, 50, was not under surveillance given he was a known extremist and had a dubious past record.

Abbott described the Sydney Cafe siege as an act of a deeply unstable person with a long history of violence and mental illness.

"This was the act of someone who is way beyond any mainstream – any mainstream – and has been rightly, absolutely repudiated by all of the communities of Australia," the Prime Minister said.

In an interview to ABC, Abbott said that there were many questions which the government would look at.

On the query of why the gunman, who was accused of several offences, was  free, Abbott said that he was also concerned and wanted to know about it.

"These are the questions that we will be asking ourselves, these are the questions that we will be having our officials ponder because he was a person who had been of interest to our security agencies, he was a person who was very well known to New South Wales police," Abbott said.

Abbott said even if there was close watch on Monis there was a possibility that the siege could not have stopped.

"Even if this individual, this sick and disturbed individual, had been front and centre on our watchlists, even if this individual had been monitored 24 hours a day, it's quite likely, certainly possibly, that this incident could have taken place because the level of control that would be necessary to prevent people from going about their daily life would be very, very high indeed," he said.

Prime Minister stressed that the attack was an isolated one.