A security official with knowledge of the police operation to foil an Anzac Day terror attack says the plot involved running a police officer over and then killing him with a knife.

Those behind the plot then planned to take the officer’s gun and go on a shooting rampage that would have ended in their deaths, the official told ABC’s 7.30.

Australian counter-terrorism officials are investigating links between the most senior Australian with the Islamic State terror group, Neil Prakash, and the group of Melbourne teenagers who were targeted in Saturday’s raids.

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Twenty-three-year-old Prakash, of Fijian-Indian and Cambodian background, is an Islamic convert and travelled to Syria in early 2013, where he took the nom de guerre Abu Khalid al Cambodi.

He is now the chief recruiter of Australians for ISIL, filling the void left by the death of Mohammed Ali Baryalei in fighting last year.

“It seems that Prakash has stepped in as the Baryalei Mark II, and that’s significant,” Greg Barton, director at Monash University’s Global Terrorism Research Centre, said.

“That makes him, like Baryalei before him, the highest ranking Australian within Islamic State we’re aware of.”

Authorities believe Prakash was crucial to the Anzac Day plot.

“Islamic State is sort of like a comet with a long tail – it’s got a very tight nucleus then a long diffuse tail,” Mr Barton said.

“It looks as if Prakash is right in that nucleus.

“And the core media group there (in Syria) is their media council, he would seem to be involved with them and their recruitment body.

“So, presumably whatever he is saying is very much coming from the upper levels of command.”

Those behind plot had links to Al Furqan: police

Police said the men involved in the alleged plot all had links to the controversial Melbourne Islamic centre, Al Furqan.

Sevdet Ramdan Besim, 18, of Hallam, was charged on Saturday. Photo: AAP

“Al-Furqan and a number of other centres around Australia have come to our attention,” Victoria Police Assistant Commissioner Steve Fontana said.

“It’s more about some of the individuals who are opening up or trying to influence these young people, they are the people of real concern.

“(The people) who have probably got those extreme views and are trying to recruit and engage others in activity.”

One of those arrested, Sevdet Besim, was charged with conspiring to plan a terrorist attack.

Another, who cannot be named, is being held on a preventative detention order.

Police also charged a third man with weapons offences.

In Britain, Manchester police arrested a 14-year-old boy in relation to the plot, saying they had allegedly uncovered communications between the teenager and a man in Australia.

One of the young men targeted, though not charged, in the raids was Eathen Cruse.

He denied any link to terrorism and said he knew nothing of any plot.

“I don’t support terrorism, I don’t want to kill innocent people, it’s not part of my religion,” Mr Cruse said.

Mr Cruse did admit to being a close friend of Numan Haider, who was shot dead outside a Melbourne police station last year after allegedly attacking police with knives.

Haider had been attending Al Furqan Islamic centre.

Mr Cruse acknowledged he was deeply shocked by Haider’s death.

“He was a generous guy, he gave to others, he was loving,” he said.

“He never treated you bad, always made you feel good. It upset me. He was one of my best friends.”

– ABC