Detectives have arrested one of Victoria's most senior suspected organised crime bosses, Rocco Arico, in raids this morning.

The Purana organised crime taskforce has been investigating the multi-millionaire over allegations Arico is involved in an extortion attempt.

Fairfax Media can reveal that the Australian Crime Commission has described Arico as one of Victoria's top ten 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 banned Arico from attending Crown Casino or Victorian racetracks over the 36-year-old's suspected organised crime activity.

Arico is a close associate of drug traffickers and known Melbourne underworld identities, including figures with links to Melbourne's Calabrian mafia cell.

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

Williams was bashed to death in Barwon prison in 2010 by one of his cellmates, Matthew Johnson.

Police suspect that prior to Williams' murder, 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 Mladenic.

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. Arico's wealth is estimated at at least $10 million.

The nation's unexplained wealth legislation is regarded by police as deeply flawed and has not been used successfully on any criminal identities, including Arico.

Land title searches conducted by Fairfax Media reveal that Arico owns a multi-million 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 and accused police of subjecting him to a witch hunt.

In 2001, Arico was jailed for a minimum of seven years for attempted murder. The charges related to an incident in which Arico repeatedly shot another man after a road rage dispute.

After the shooting, Arico attempted to flee Victoria and was driven to the airport by Carl Williams.

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.