SYDNEY, Dec. 23 (Xinhua) -- Australia remained on alert over the holiday period after authorities arrested seven people on Friday allegedly planning a Christmas Day terror attack.
A staunch ally in the U.S.-led fight against terror in Syria and Iraq, Australia has remained on heightened alert for home-grown terror attacks for over two and a half years, arresting or jailing at least 57 suspects from 25 counter-terrorism operations.
The country however has seen four terror attacks despite 12 successful disruptions, including the murder of police accountant Curtis Cheng in November 2015.
Authorities on Friday raided several properties in Victoria state, arresting five self-radicalized men aged 21 to 26 years old for allegedly preparing a multi-mode terror attack targeting downtown Melbourne using explosives and other weapons, possibly on Christmas Day.
Two others, a 20-year-old woman and 26-year-old man were arrested, but later released without charge.
"In terms of events that we have seen over the past few years in Australia, this certainly concerns me more than any other event that I've seen," Australian Federal Police Commissioner Andrew Colvin told reporters in Sydney on Friday.
Melbourne's iconic Flinders Station, Federation Square and St Paul's Anglican Cathedral were the likely targets, police said.
Australian authorities have remained on alert for a Christmas Day plot following Indonesia's Special Detachment raids that killed three terrorism suspects in West Jakarta on Tuesday and recent attacks in Europe where trucks have rammed into large celebratory gatherings.
"Islamist terrorism is a global challenge that affects us all. But we must not be cowed by the terrorists," Australian Prime Minster Malcolm Turnbull said.
"I can assure all Australians that our police services right across the country, our intelligence agencies right across the country, and around the world, are at the highest state of alert."
Though Islamic State inspired, there is no link between events in the past week and Friday's raids.
Commissioner Colvin believes authorities have removed "the bulk of this particular cell," though "they have associates that we are always interested in, and there's a number of people ... in this country that we have a remaining security interest in."
Police presence will be enhanced across Australia for public events, such as the New Years Eve fireworks in Sydney, Christmas Eve carols in Melbourne and the Boxing Day Test at the Melbourne Cricket Ground (MCG).
But Turnbull said Australians shouldn't give into terrorists, "to cow us into abandoning our Australian way of life" and "go about their lives in the normal way.
"They want to frighten Australians. They want to divide Australians. They want us to turn on each other. We will not let them succeed," Turnbull said.