Worship without fear: Melbourne Archbishop

Melbourne's Anglican Archbishop has encouraged parishioners to worship without fear after St Paul's Cathederal was named as one of three targets in an alleged Christmas Day terror attack.

Five people will appear in court on Friday with police saying they planned to use explosives and weapons to attack the cathedral, Flinders Street Station and Federation Square on Christmas Day.

Following the arrests it was generally business as usual at the three venues.

Worshippers attended St Paul's 12.15pm church service on Friday.

"I've been told by Victoria Police that the threat level is no greater enhanced now that a terrorist plot has been foiled," Anglican Archbishop Dr Philip Freier told reporters.

"We look forward to continuing our worship on Christmas Eve and Christmas Day unaffected by these things and I'd encourage people who are planning to come and worship with us at St Paul's cathedral to do so."

Services will continue as scheduled but with extra security in place.

There was a heightened police presence at Federation Square on Friday with at least half a dozen police extra officers deployed.

"We're here to reassure the public and to make them feel safe," an officer told AAP.

Thousands of commuters continue to file through Flinders Street Station with many at first unaware of the police raids that led to the arrests.

Lizzie Hains, 18, was waiting for a friend at the station when she heard the news.

"That's so scary - I actually feel sick," she told AAP

"It makes me feel a bit unsafe."

Train services will operate as usual over Christmas and the New Year.

"There is no change to the previously scheduled services over the holiday period," a Public Transport Victoria spokesman told AAP.

Visitors continue to attend the National Gallery of Victoria at Federation Square too, with staff saying the gallery was open as usual.

It will shut on Christmas Day only as it does every year.