ASIO tip-off claim to be reviewed: Abbott

A call to the national security hotline about gunman Man Haron Monis did not expose his deadly plan, Prime Minister Tony Abbott says.

The tip-off was followed up, but Mr Abbott says it didn't reveal the imminent Sydney siege attack.

"The information provided didn't expose any threats of direct violence by the Martin Place murderer," he told reporters.

"It was followed up, it was really followed up."

The comments come after claims ASIO was forewarned about the self-styled sheikh's extremism by an anonymous caller.

The prime minister said a joint review between the federal and NSW governments will go through the siege events to determine what happened before, during and afterwards.

NSW Premier Mike Baird said the review was aimed at ensuring such a tragedy does not recur.

The premier did not comment on ASIO's involvement and put the blame solely on Monis.

"It is something that all of us have a heavy heart over but we have to go through this because we need to ensure every measure is taken to ensure it doesn't happen again," Mr Baird told reporters.

"But I will say, there is one person who is responsible for the actions that happened in the past week and we know who he is. He came with an intent to divide this city but what he has done is united the city."

The caller did not suggest that Monis had a gun or that he was planning a terrorist act or that he had talked of any plans to take hostages but urged officials to "take a look at this man's website".

ASIO is understood to have looked at Monis's website as result of the phone call.