Police are investigating links between a Melbourne teenager charged following terror raids, and overseas extremists.

The 17-year-old boy was arrested and charged with terrorism-related offences after a dramatic raid at a home in Melbourne’s north on Friday.

Police say the Greenvale raid foiled an “imminent” threat to the community after a tip-off to the national security hotline.

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Victoria Police Acting Chief Commissioner Tim Cartwright said police were looking into possible links with extremists.

“We’re trying to find out how the young man became radicalised,” he said.

“We continue to look for linkages. We also look to try and identify what it is that led this man to this situation.”

The teen remains in custody and is expected to appear in court on Monday.

Police have refused to comment on reports the alleged attack was planned for Mother’s Day and there was “no specific intelligence identifying any events as targets”.

They also urged against speculation that could incite fear.

However, Mr Cartwright said the 17-year-old was allegedly “well advanced” in preparing a bomb.

“We do believe the young man intended to explode a device at an event over the coming days,” he told reporters on Sunday.

“We will allege he had taken serious steps to prepare a device and … we made the judgment call late last week that in the interest of public safety we needed to act, and we did.”

Mr Cartwright said overseas recruiters remained a “real challenge” for police.

“A challenge we haven’t seen in the past,” he said.

“The internet provides people the opportunities to radicalise from across the world. It is a real concern for us.”

The boy’s family had been relocated as police conducted a “long and meticulous” search of their home. It is an effort expected to continue into Monday.

“In this case, as is often the case, families are as much a victim as the rest of the community,” Mr Cartwright said.

“They are shocked and surprised. We are doing everything we can to support the family.”

The teenager’s older sister told the Sunday Herald Sun it was unlikely he had been influenced by others because he had few friends outside the family.

“He is kind, gentle and softly spoken,” she said.

Mr Cartwright said police did not expect any further arrests and the teenager had co-operated with police since being taken into custody.

He said the increased police presence at major events was the way of the future since the public alert level was raised, and Victorians should remain alert.

“If you see anything suspicious, if you see young people take an unusual interest in what would normally be household devices, electricals, chemicals, then you need to be concerned, you need to tell us,” Mr Cartwright said.