An international drug syndicate used drones to conduct counter-surveillance on police before seven members were arrested in Melbourne over a $30 million shipment of cocaine from Panama, authorities say.

Key points: Drug syndicate used drone during meetings to see who was watching

Drug syndicate used drone during meetings to see who was watching Seven men from from Australia, Britain, Canada arrested

Seven men from from Australia, Britain, Canada arrested Police worked with authorities in South America, North America, Asia

Police said the men — four from Australia, one from Britain and two from Canada — were arrested on Thursday after the drug shipment arrived three days earlier.

"On Monday evening a cargo vessel, The Spirit of Shanghai, arrived in the Port of Melbourne from Panama," Commander John Beveridge from the Australian Federal Police (AFP) said.

"The particular container we were interested in possessed three black duffel bags placed inside the container with a duplicate seal.

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"Each bag contained 26 boxes of cocaine. The amount of cocaine is estimated at a street value of $30 million."

On Thursday, officers raided 12 properties across Melbourne, arresting the men in Essendon, Carlton and South Yarra. They also seized $580,000 in cash, they said.

They have been charged with drug trafficking and money laundering offences.

"During the investigation phase, this syndicate has used aerial drones to conduct counter-surveillance on police activity," Commander Beveridge said.

"The syndicate was using a drone when they were holding their meetings, to conduct counter-surveillance, to see if anyone, like law enforcement, was watching.

"We haven't seen a lot of it. It has been used before. This syndicate did deploy it quite often.

"It did cause the surveillance staff to initiate procedures and methodologies to defeat it.

"These syndicates are getting a lot more sophisticated, and so are we. We've just got to be awake to it."

Drug demand 'through the roof'

The drugs seized had a street value of $30 million, police said. ( ABC News: Joanna Crothers )

The police operation involved a number of forces around the world.

"We've been acting with our counterparts in North and South America and throughout Asia throughout this investigation," Commander Beveridge said.

Australian Border Force (ABF) Acting Assistant Commissioner James Watson said the demand for drugs in Australia was growing but authorities were making inroads.

"They're going through the roof. We are detecting more illicit substances at our border than ever before," he said.

"This is thousands of hits of cocaine that won't reach vulnerable Australians, and it's millions of dollars that won't be funnelled back into criminal syndicates' pocket.

"It's a very sophisticated and well-planned attempt by criminal entities to import a large quantity of cocaine into Victoria."