At least 27 people have been arrested in a series of raids in Melbourne's western suburbs aimed at Middle Eastern organised crime gangs.

About 700 police officers were involved in Operation Skyborne set up by the Santiago Taskforce.

Police seized drugs, firearms, cash, ammunition, vehicles and stolen property in the pre-dawn raids on 44 properties in Altona North, Williamstown, Truganina and Sunshine.

The warrants were issued by the Santiago Taskforce, which was set up in 2008 to investigate organised crime and non-fatal shootings involving a number of families and their associates.

Neighbour Chris heard loud motorbikes around 1:30am.

"It's not the first time that the police have been here. Put it that way," he said.

Assistant Police Commissioner Stephen Fontana says intelligence gathered by Victorian and federal investigators suggests the crime gang was heavily involved in trafficking methamphetamines and firearms.

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"We've seized over 100 kilos of dried cannabis," he told ABC local radio.

"We're currently at a property in Moorabool where we're pulling out over 35,000 tobacco plants.

"We've seized nine firearms, a large quantity of ammunition, large quantity of cash and other stolen property."

Police pulled out 35,000 tobacco plants at a property at Moorabool, near Geelong, which is connected to the raids. ( ABC News: Margaret Paul )

Extra police back-up, including the special operations group (SOG), were brought in for what police called the "risky operation."

"We had about six high risk arrests. The SOG was deployed for three of them," Mr Fontana said.

"We're very happy that this operation has run relatively smoothly.

"No-one has been injured which is a real bonus when you're looking at such a high risk group of individuals that we were targeting."

Seven people faced court this afternoon charged with various offences including weapons, drug possession and trafficking offences.