One year on, Sydney's Martin Place remembers siege

Australians marked the one-year anniversary of a cafe siege by a self-styled Islamic cleric which left two hostages dead and shocked the nation with a message of unity on Tuesday.

At a twilight ceremony outside the cafe in Sydney's Martin Place, Prime Minister Malcolm Turnbull said the events of December 2014 had left the city grieving.

But he said in response that "a whole nation resolved to answer hatred with love... To answer those who seek to divide us with solidarity".

The Lindt cafe building in which the siege took place was lit up Tuesday evening with projections of floral tributes and messages of support and unity.

Sydneysider Mary Gandy, among hundreds of members of the public attending the memorial, said the siege struck a chord with Australians.

"When you get something like this you've got to show your support," she told AFP of attending the tribute.

Iranian-born Man Haron Monis began the siege in the upmarket chocolate cafe in the city's financial hub Martin Place early on December 15, 2014, taking staff and customers hostage for 17 hours.

The siege ended after Monis, who was armed with a pump-action shotgun, shot dead 34-year-old cafe manager Tori Johnson.

Tactical police stormed the building, killing Monis while Katrina Dawson, a 38-year-old barrister and mother of three, died after being hit by a ricocheting police bullet or fragment.

The crime horrified Australia, prompting thousands of people to leave bunches of flowers in Martin Place in the following days, in an impromptu outpouring of emotion which transformed the pedestrian strip into a "sea of colour".

New South Wales Premier Mike Baird said while the crime was a "senseless and horrific act of terror", Australia's reaction would be remembered.

"Something remarkable happened here. As a city we were drawn to Martin Place. We came in shock and in sorrow but every step we took was with purpose," he said.

"And it was clear to the world that Sydney stands together. We had faced hate and horror but we responded with love and defiance."

A permanent memorial will be established in which stylised flowers will be embedded inside the pavement of Martin Place, he added.

An inquest into the siege is not yet complete, but State Coroner Michael Barnes said that one year on, many people were still upset.

"It is important to remember this is the first time in Australia a coronial inquest has examined a potential act of terrorism," he said in a statement.

Australia raised the terror alert level to high last year and introduced new national security laws amid increasing concern over home-grown extremism.

"We, as law enforcers, will do absolutely everything we can to prevent this type of thing happening again," New South Wales police commissioner Andrew Scipione said ahead of the memorial.