Police by Sydney's side in siege aftermath

They have seen the fear in people's eyes but NSW police want Sydneysiders to know they are safe.

Hundreds of police have hit the streets around the city's popular locations, including Martin Place and Circular Quay, after Sydney's fatal siege.

Assistant Commissioner Michael Fuller said police had noticed the huge numbers of friends, families and strangers flocking to Martin Place since the hostage situation gripped the city on Monday.

"We see the fear in their eyes and we want to let them know that we are out there to know they are safe and they can go about their business like normal," he told reporters on Wednesday.

The increased round-the-clock policing, part of Operation Hammerhead, comes as a man was charged for allegedly threatening to destroy the Auburn mosque on Tuesday.

The 30-year-old allegedly called the mosque and made a number of threats.

Police arrested him in Dural in Sydney's northwest and he was charged with four offences, including threatening to destroy property.

The 30-year-old was granted bail to appear in court next year.

Mr Fuller said there had been some issues of hate and bias crime but said it was minimal compared to the outpouring of support.

"You have all seen the flowers down at Martin Place," he said.

On Wednesday officers remained at the Lindt cafe in Martin Place examining the scene of the fatal siege.

It's expected the crime scene examination could wrap up by Wednesday afternoon, Mr Fuller said.

"We are anticipating hopefully by the end of today the crime scene will be handed back to the owners of the store," he said.

A very experienced detective inspector is carrying out the critical incident investigation into the siege, Mr Fuller said.

But there is no time frame on when it would be completed, he added.