Detectives will move to seize an estimated $10 million in assets belonging to a man suspected of being one of Victoria's most senior organised crime bosses, Rocco Arico.

The revelations come after police on Thursday night charged Arico with extortion and blackmail and remanded him into custody.

Police have been investigating the multimillionaire over the alleged extortion since 2013, after earlier investigations into Mr Arico for drug trafficking, money laundering and murder failed to lead to any charges.

On Thursday morning, Purana organised crime taskforce detectives raided a number of properties connected to Arico, including a Lygon street cafe and his inner city high-rise apartment.

The charges are understood to relate to alleged threats he made to an associate, including demands for a large amount of money.

Investigators from the force's criminal assets division were part of the investigation into Mr Arico, who is also facing assault, drugs and weapons charges.

Mr Arico is a former close associate of Carl Williams – and police suspect him of helping to arrange Williams' murder in Barwon prison in 2010.

Arico has been a target of multiple state and federal policing agencies, although he has previously accused the police of hounding him and claims his wealth has been legitimately earned.

Fairfax Media can reveal that the Australian Crime Commission has alleged that Mr Arico is one of Victoria's top 10 criminal figures in a confidential assessment of the most serious organised crime threats facing the nation.

Fairfax Media can also reveal that former Victoria Police chief commissioner Ken Lay last year banned Arico from attending Crown Casino or Victorian racetracks. The ban was issued in connection to the 36-year-old's suspected organised crime activity.

Mr Arico is a close associate of drug traffickers and known Melbourne underworld identities, including figures with links to Melbourne's Calabrian mafia cell. One of his relatives is suspected to be an influential member of the cell.

Earlier this year, Fairfax Media and the ABC Four Corners program revealed Arico was suspected by police of helping to organise the murder of his former close associate Williams.

Williams was bashed to death in Barwon prison in 2010 by a cellmate, Matthew Johnson.

Police suspect that prior to Williams' murder, Mr Arico was concerned that Williams – who was assisting police in the investigation of unsolved gangland murders – might implicate him in the 2000 slaying of underworld identity Richard Mladenich.

Arico was the first person outside of Barwon prison to learn of Williams' death after another of Williams' cellmates phoned Arico several minutes after the murder.

State and federal organised crime investigators have previously sought legal advice about whether they could use unexplained wealth legislation or asset confiscation laws to seize millions of dollars of property owned by Arico.

The legislation is regarded by police as deeply flawed and has not been used successfully on any criminal identities, including Arico. However, it is easier to seize the assets of a person once they are charged.

Land title searches conducted by Fairfax Media reveal that Arico owns a multimillion dollar property in Brighton, on the Mornington Peninsula and in Melbourne's northern suburbs.

He has previously described himself in the media as a developer and builder.

In a statement, police said that detectives had "located a semi-automatic pistol, ammunition and a quantity of cash" at a property linked to Arico.

"Purana Taskforce detectives believe the alleged blackmail and extortion began in 2013 and continued through to current times," the statement said.