drug bust raid sieze amphetamine
Police in Melbourne, Australia siezed $15m worth of methamphetamine in one of their biggest drug raids in 10 years. REUTERS

Police in Melbourne, Australia have found up to AU$15 million (£12m) worth of pure amphetamine during a series of coordinated drug raids on Tuesday.

Four men between the ages of 22 and 36 have been arrested in relation to the incident and have remained in custody facing drug and other charges.

Police raided properties in the suburbs of Maribyrnong, St Leonards, Brunswick, Ascot Vale and Hawthorn where they located hidden drug lab equipment, guns and more than $150,000 in cash.

At a housing development in Maribyrnong, two men barricaded themselves inside a flat. They were arrested after a five-hour stand-off.

Raids at three other addresses resulted in another two arrests.

Police said one of the men arrested was wanted in New South Wales and Queensland.

But it was a farmhouse in St Leonards on the Bellarine Peninsula that was the focus of the operation.

It was discovered that the entire house was filled with chemicals, with every room inside used for part of the drug manufacturing process.

Detective Superintendent Doug Fry said this was the biggest of a series of labs they've linked to the arrested men.

"It is very substantial, very sophisticated and at the moment it appears that it is turning out 15 to 20kg in one cook," he told Reuters.

"Anyone who is trafficking these sorts of quantities of methamphetamine invariably has a connection to significant organised crime."

The operation has been described as on the same scale of Melbourne drug criminals Tony Mokbel and Carl Williams.

The raids were a culmination of a six month long investigation and police said their laboratory squad classified this as one of the most sophisticated drug labs they have seen in last decade.