Australian parents on terror alert

Members of the bomb squad carry a device to a sand bagged area to be detonated as terror raids are carried out in Greenvale in Melbourne. Photo / AAP

Australian police have urged parents to keep a closer eye on their children and monitor social media activity, after foiling yet another alleged teenage terror plot.

A 17-year-old who was allegedly planning a Mother's Day attack in Melbourne will face court today over two terror-related offences.

Police reportedly found three home-made pipe bombs in his bedroom at the family home in the well-to-do suburb of Greenvale, following a tip-off late last month to Australia's National Security Hotline.

The Deputy Commissioner of the Australian Federal Police (AFP), Mike Phelan, said on Saturday that he could "absolutely guarantee" lives had been saved as a result of the raid carried out by dozens of counter-terrorism officers on Friday afternoon.

"We may not know exactly where it [an attack] was going to occur, nor when it was exactly going to occur," said Phelan. "But let me tell you, something was going to happen, and as a result of Victoria Police and AFP interception yesterday some Victorians are going to be alive because of it."

As police continued to search the family home yesterday, they declined to confirm that the teenager had planned to target one or more Mother's Day events in the Melbourne CBD. But they said that thanks to Friday's raid there was "no longer an imminent threat" to the public.

This latest incident was not connected to alleged plans to behead a police officer, steal his gun and carry out a shooting rampage at an Anzac Day commemoration in Melbourne last month, police say.

Teen arrested as police detonate explosive devices after Melbourne raids. Full details at 7am. #Today9 pic.twitter.com/jQcsRtodU3

— The Today Show (@TheTodayShow) May 8, 2015

Police raids underway in Melbourne http://t.co/AX8iZUXVw0 pic.twitter.com/kZne5wnGVi

— SBS News (@SBSNews) May 8, 2015

Three teenagers have been charged over that affair, as has a 14-year-old boy in northern England.

The identity of the teenager arrested on Friday has been suppressed, but according to the Sunday Herald Sun the family are Syrian migrants and the father is a doctor. The boy's 21-year-old sister said he was a quiet boy who "would not hurt a fly".

On his Facebook page, he had written that Muslims should hate "kafir" (unbelievers) and that followers of Shia Islam were "not human". He reportedly blocked his parents and extended family from viewing his posts.

Phelan said that however hard security agencies worked to detect and track disaffected and potentially dangerous young Muslims, they also needed the help of "family, friends, schoolmates, teachers [and] peer groups".

The latest arrest was a "sobering reminder" of the importance of parents engaging with their children, he said, adding: "It is usually the families and friends that are the first to have indicators of this kind of activity." The teenager's sister told the Sunday Herald Sun he was a "kind, gentle and softly spoken" person who "never raises his voice" and wanted to follow his father into the medical profession.

She dismissed his online comments, saying: "He's 17, it's just him being a keyboard warrior." The Victorian Premier, Daniel Andrews, said police had briefed him "many times" on their counter-terrorism operation since the tip-off on April 30.