Detonations follow Melbourne terror raids

Police have detonated two improvised explosive devices following a dramatic counter-terrorism operation in Melbourne's north.

A loud blast could be heard shortly after 8.30pm on Friday at a public reserve near a house in suburban Greenvale which had been the focus of a high-level search involving state and federal police throughout the afternoon and evening.

A second explosion erupted about an hour later.

Before the controlled detonations, police extended a 300m metre exclusion zone around the residence and sent a robot inside along with heavily-armed bomb squad officers.

A number of explosive devices were located at the Clare Boulevard house, a police spokesman confirmed. It had since been rendered safe.

Police warned earlier of imminent "action" at the home.

Teams of officers placed Greenvale in lockdown as bomb squad officers and sniffer dogs began scouring the two-storey home shortly after 12.30pm.

Others, many wearing balaclavas and armed with assault rifles, swarmed surrounding streets, as a no-fly zone was declared overhead.

Witnesses told the Nine Network police shortly after used a loud speaker to demand the occupants come out.

A man emerged, walking into the street with his hands behind his head.

Six women followed and were escorted away.

Police have refused to say whether anyone has been arrested, why they launched the operation or who they were targeting.

One man who lives near the house, and who gave his name only as Bilal, said he heard what sounded like gunshots before dozens of armed officers arrived.

"They couldn't tell us nothing, they just said there were believed to be explosives in the house," he told Network Ten.

Other witnesses say they saw two men led away by officers into an unmarked police car.

Greenvale resident Jack said he'd seen a similar scene several weeks ago in a nearby street.

"It makes me feel uncomfortable and not safe," he told AAP.

Dianna, who lives a minute from the house, told AAP it was "terrifying".

"I hate not knowing what's going on, it's usually a really quiet place to live."

Victoria Police would only confirm the joint exercise with the Australian Federal Police was part of an "ongoing operation".

It was widely reported on Friday that simultaneous raids were launched in other of Melbourne's northern suburbs. A large police presence was reported in the nearby suburb Coolaroo.

It is not known whether the latest raids are linked to Operation Rising, which saw 200 heavily armed officers storm properties in the city's southeast on April 18, over an alleged Islamic State-inspired terror plot planned for Anzac Day.

In those raids, five men were arrested and three later charged.

Friday's raids follow orders overnight from police command enforcing new rules for officers, which mandate they cannot work alone, must wear bulletproof vests and be armed during work hours.