One-of-three Melbourne terror suspects had become increasingly isolated in recent years, praying at home instead of attending a local mosque, a neighbour says.

A 30-year-old man arrested during a series of raids across the city's northwest on Tuesday had stopped going to the nearby Broadmeadows Mosque, Zubair Mohamed said.

"I have been not hanging with them now maybe two years," he told ABC TV.

"Used to be we go and pray together and go and have a coffee. Since two years ago, they just pray themselves at home."

"He got a few friend and pray in the house. I don't agree with that. We pray not for any group, only to the one god ... I telling them 'you guys doing something wrong. There is a mosque close by. We go pray in the mosque'."

Mr Mohamed said the the suspect was "not political, just a normal person".

"I don't see anything political. I don't know what's in his head."

Police said the wives and children of the suspected terrorists were at the properties when raids were carried out.

A woman at the Dallas address where the 30-year-old man was arrested, declined to speak about details with reporters.

"I am not in the mood to talk," she told the Herald Sun.

"I don't know what happened."

A strong police presence remained at each address.

A 21-year-old Greenvale man has been charged with planning a terrorist act while the 30-year-old and a 26-year-old from Campbellfield continues to be questioned by police.