1st LD Writethru: Australian police arrest two suspects in counter-terror raids

Australian counter terrorism police on Thursday arrested a 20-year-old man and a 15-year-old teenager accused of plotting an attack on a government building last year.

Authorities confirmed three others, already in custody from counter-terrorism raids in December 2014 as part of Operation Appleby, will also be charged in relation to the conspiracy later in the day.

It is alleged the two men helped formulate the seized documents obtained in counter-terrorism raids in December on an alleged plot to kill a member of the public or attack a government building, namely the Australian Federal Police headquarters in Sydney.

"There is no new threat. These (arrests) are definitely related to the activities of December 2014," Australian Federal Police (AFP) deputy commissioner for national security Michael Phelan told reporters, though noted heightened security outside the AFP's headquarters and other Sydney police stations.

Australia has been under heightened alert for attacks by home-grown radicals since Operation Appleby was launched in September last year, which so far has resulted in the arrests of people - 11 in Sydney alone - in connection with domestic terror plots.

Phelan negated questions regarding any possible links to Islamic State, saying the group has the capacity and intent to carry out a terrorist attack without external influences.

Though no direct link, a group who are believed to be associates of those arrested on Thursday had internally radicalised a 15-year-old teenager who murdered police accountant Curtis Cheng in early October.

"It's disturbing that we're continuing to see teenage children in this environment," New South Wales police deputy commissioner for specialist operations Catherine Burn said.

In September 2014, police shot dead a teenager after he stabbed two counter-terrorism police officers outside of a Melbourne police station.

The raids came less than a week before the anniversary of the Sydney Siege where two hostages were killed when police stormed the Lindt Cafe in Sydney's Martin Place, killing the gunman. Enditem