A Charles Sturt University (CSU) counter-terrorism expert says it is significant that the Prime Minister of Australia has commented on increased 'terrorist chatter' ahead of Christmas.

Associate Professor Nick O'Brien, the Head of School at the CSU Australian Graduate School of Policing and Security, says, "While there does not seem to be specific information about a terrorist attack, an increased level of terrorist chatter is sometimes the precursor to an attack.

"The terrorist threat level remains at 'high' which means that 'a terrorist attack is likely', and people should continue to be vigilant during the festive season."

Professor O'Brien says 'terrorist chatter' is a term used by security agencies to describe the intelligence received from a number of sources including the interception of communications. It could also include information received from other countries which are monitoring terrorist targets that may have connections to Australia.

Prime Minister Tony Abbott has warned of a 'heightened level of terrorist chatter'. These comments were made following a briefing from the security agencies and the Australian Federal Police at a National Security Committee of Cabinet.

Professor O'Brien noted that two men have also been arrested in Sydney by the joint counter-terrorism team and one of them has been charged after allegedly having been found in possession of documents designed to facilitate a terrorist attack. A senior member of the Australian Federal Police has apparently stated that the documents referred to "potential government targets" in Sydney.

Associate Professor Nick O'Brien is available for media interviews on 0419 248 387.