Australian police said Thursday that they arrested a man in connection with suspected terrorism offenses during raids in which they seized firearms, computer equipment and a USB stick containing what they said were "violent extremist materials."

Officers swooped onto properties in six Melbourne suburbs Wednesday in a simultaneous raid, the Australian Federal Police and Victoria state police said in a joint statement. The name of the 23-year-old man they arrested was not released.

Among the police targets was an Islamic bookstore called the Al-Furqan Islamic Information Centre. The center's representatives did not respond to calls and emails Thursday, though a spokesman on Wednesday confirmed that police spent about 12 hours inside and took several items.

Steve Fontana, Victoria police assistant commissioner for crime, said police had identified no immediate threats to public safety.

"We will continue to work to ensure that all steps are taken to protect all members of the community," he said.

The man who was arrested was expected to be charged Thursday with collecting or making documents likely to facilitate terrorist acts. If convicted, he could face a maximum sentence of 15 years in prison. Police said he was hospitalized with stomach pains on Thursday morning.

On its website, the Al-Furqan center says it hosts an Islamic book store and library and offers youth activities, daily prayers and classes.

Terrorism expert Greg Barton, director of Monash University's Centre for Islam and the Modern World, said the Al-Furqan center represents the "fringe of the fringe."

"Their talk is extreme on their website _ they've got a link to an interview with Anwar al-Awlaki, the former Yemeni-American leader to al-Qaida," he said. "So there's no question they're flying their colors in a fairly flagrant fashion."

Still, the group only attracts a few dozen regular members, has no broad influence and had garnered little attention until Wednesday's raids, Barton said.

"They'd ordinarily be a group that's all talk and no action except for the possibility somebody might take on board their ideas and move on and go abroad," Barton said. "It's got stepping stone potential, I think, which is why the authorities were watching them."

Over the past few weeks, the group made several postings on its Facebook page and website referencing a "spy" that had been uncovered in their community. It was not clear from the postings what specifically the group was referring to.

Barton said he suspects that once the group began posting publicly about being under surveillance, authorities decided to move in.

Police declined to comment on the spying allegations.