Tony Mokbel.

Tony Mokbel. Photo: Jason South

Gangland drug boss Tony Mokbel is under police investigation for allegedly attacking another inmate at Barwon Prison.

A prisoner aged in his 30s suffered a broken nose during the alleged attack on Thursday last week, a Corrections Victoria spokesman said.

Paramedics were called to the prison, near Geelong, and raced the injured inmate to hospital for treatment.

Victoria Police is investigating the incident.

It is not known what sparked the alleged attack.

Mokbel, 48, is in the maximum-security prison serving a minimum of 22 years for masterminding a multimillion-dollar drug trafficking empire.

He became Australia's most wanted fugitive after skipping bail in March 2006 and fleeing to Europe while facing serious drug charges.

Mokbel pleaded guilty in 2011 to trafficking large commercial quantities of methamphetamine and MDMA, and inciting an undercover policeman to import a commercial quantity of MDMA.

He made millions of dollars through an international drug operation, known as The Company.