Amid the sea of flowers and mourners at Sydney's Martin Place, siege survivor Harriette Denny set up her own tribute for her slain boss, Tori Johnson.

The frontier city of Peshawar was once known as "the city of flowers".

The "fake sheik" behind the deadly Sydney cafe siege railed against Australian "terrorism" on his website a day before he took 17 people hostage.

PM John Key said the Sydney siege gunman highlighted the conundrum for authorities over protecting citizens against potential terrorism and over-stepping their powers.

Government MP Mark Mitchell argues that the Sydney hostage drama is 100 per cent justification for the anti-terrorist legislation he helped bulldoze through Parliament last week.

Prime Minister Tony Abbott will urgently review how a lone gunman known to federal police and ASIO was able to take hostages in a Sydney cafe.

There was Bali, but it was Westerners - not Australians, specifically - who were targeted.

Against a backdrop of fear and uncertainty following the hostage taking in Sydney, thousands of ordinary Australians turned to social media to spread a message of unprecedented tolerance and solidarity.

These are the six words that say it all. "I'll be back at work tomorrow."

Whenever there is a dramatic event, social media instantly comes alive with comment and conjecture as facts vie for attention with fiction.

Hostages caught in Sydney's siege have revealed how some of them managed to escape when the gunman's back was turned.

Haron Monis was known to authorities for a string of offences.

The country’s highest Islamic office holder has condemned the actions of a gunman responsible for a hostage situation in Sydney’s CBD.

Some hostages held in the Sydney cafe may have had thoughts of attacking the hostage takers as survival instincts "come to the fore", a psychologist says.

The MP who chaired the anti-terrorist legislation rushed through Parliament last week, MarkMitchell, says the bill was "100 per cent" justified.

Could it happen here? That is a question to haunt this country whatever the outcome of the hostage crisis in Sydney.

A flurry of loud bangs erupted just after 4am NZ time as a swarm of heavily armed police stormed a downtown Sydney cafe where a gunman had taken hostages.

As the Sydney siege threatens to open up old prejudices, hashtag #illridewithyou has led a call for unity.

Here's what we know now about the situation in Sydney where a gunman has seized hostages.

Read how the Sydney siege unfolded during the day.

New Zealanders caught up in the area where a hostage drama is unfolding in central Sydney - some who are still in lock down - have spoken about their experiences.

The cafe siege in Sydney was only to be expected after Islamic State urged followers to launch such “lone wolf” attacks, specifically mentioning Australia, terror experts say.

Martin Place in Sydney CBD is in lockdown after gunmen took hostages at the popular Lindt cafe this morning.

Parliament has just passed legislation aimed at stopping would-be foreign fighters from leaving New Zealand to join Islamic State in Iraq.