Mourners were to attend emotional services for the two victims of the Sydney cafe siege Tuesday as volunteers and workers removed a giant sea of flowers laid in their memory amid plans for a permanent memorial.

Iranian-born Monis, who had a history of extremism and violence, was killed after taking 17 hostages under an Islamic flag last week.

The standoff touched a raw nerve in Australia and triggered an outpouring of grief that saw thousands of bouquets laid at a makeshift memorial near the cafe in Martin Place, that grew bigger by the day.

But a week after the tragedy and storms forecast New South Wales Premier Mike Baird said the time was right to clear the area, with an army of Red Cross workers, volunteers and council officials moving in.

They collected the flowers, which will be mulched and used at a suitable site after consultation with the victim's families, along with countless notes, messages and cards, which will be preserved.

"At an appropriate time we'll also discuss with them (the families) the establishment of a permanent memorial," New South Wales Premier Mike Baird said.

Condolence books were to remain open at the state parliament and the Sydney Opera House until the end of January.

"The condolence books will be bound in several volumes and one complete copy will be provided to each family," Baird added.

A private funeral was held for Johnson on Tuesday with mourners arriving dressed in black outside the St Stephen's Uniting Church just metres from where he died.

Numerous dignitaries joined them, including Baird and New South Wales Police Commissioner Andrew Scipione, whose own family were in the cafe just moments before the siege started.

Johnson's father Ken, partner Thomas Zinn and other relatives carried the white coffin into the church.

Unity was a theme, with the Johnson family using a phrase by Persian poet Rumi on the front-page of the order of service: "Out beyond ideas of wrong-doing and right-doing, there is a field. I will meet you there."

A memorial for lawyer Dawson will be held later Tuesday, with mourners encouraged to wear aqua blue -- her favourite colour.

Monis, who was known to various authorities, was on bail at the time for a string of charges, including sexual offences and abetting the murder of his ex-wife.

The fact he was on the streets, and not under surveillance, saw Prime Minister Tony Abbott order an urgent inquiry into the circumstances surrounding the siege.