Police on Tuesday charged three men over an alleged plan to use at least one semi-automatic gun to shoot as many people as possible at an unknown crowded city location.

The plot is one in a string of threats foiled or dealt with by police and security organisations since 2014.

Asked why Melbourne was "terror central", Mr Andrews said: "This evil manifests itself in lots of different places across our nation.

"We know this is a very real issue. Very serious threats. No getting around that."

The premier pointed to the creation of Victoria's counter-terrorism command after Labor was elected to government four years ago.

"We saw the results of that work yesterday," he told the Nine Network on Wednesday.

Hanifi Halis, 21, and brothers Samed Eriklioglu, 26, and Ertunc Eriklioglu, 30, are in custody after each being charged with one count of preparing or planning for a terrorist act.

They were arrested during a series of raids across suburban northern Melbourne and were remanded in custody after facing Melbourne Magistrates Court.

Habiba Ba said her husband Ertunc Eriklioglu is a good man and not guilty of the allegations against him.

"Why would he kill people? He's a religious man," she told the Herald Sun.

The couple have spoken since his arrest and he told her not to worry.

"He's not guilty. I'm not going to believe it. How am I going to live without my husband?

"I've just given birth. What do I say to my daughter? She's been crying. Are my children going to grow up without a father? I can't eat, I can't drink."

Yasemin Eriklioglu, the mother of the accused brothers, said they were "beautiful" boys with a "gentle nature".

Assistant Commissioner Ross Guenther from the counter-terror command said events of the past fortnight, including a deadly terror stabbing in the city and a guilty finding against killer rampage driver James Gargasoulas, motivated the trio to act.

Three men were also found guilty earlier this month of planning a terror attack in Melbourne's CBD on Christmas Day, 2016.

"Sadly we had the event in Bourke Street and the James Gargasoulas trial and those events plus the ISIS propaganda machine has quite energised them towards committing an act in Melbourne," he told the Nine Network on Wednesday.

"There is no doubt that inspiration obviously for these kind of act is drawn from other sources.

"Al-Qaeda and ISIS have not come away from their propaganda machine and they have pushed hard in the last three years and that is not looking to stop any time soon."

Mr Guenther said police had to trawl through large amounts of information to identify details about the plot.

The trio returns to court in April.

Australian Associated Press